High expression of NPY receptors in the human testis

NPY receptors represent novel molecular therapeutic targets in cancer and obesity. However, the extent of NPY receptor expression in normal human tissues is poorly investigated. Based on the role of NPY in reproductive functions, the NPY receptor expression was studied in 25 normal human testes and, additionally, 24 testicular tumors using NPY receptor autoradiography. In the normal testis, Leydig cells strongly expressed NPY receptor subtype Y2, and small arterial blood vessels Y1. Y2 receptors were found to be functional with agonist-stimulated [(35)S]GTPγS binding autoradiography. Full functional integrity of the NPY system was further suggested by the immunohistochemical detection of NPY peptide in nerve fibers directly adjacent to Leydig cells and arteries. Germ cell tumors expressed Y1 and Y2 on tumor cells in 33% and Y1 on intratumoral blood vessels in 50%. Based on its strong NPY receptor expression in Leydig cells and blood vessels, the normal human testis represents a potentially important physiological and pharmalogical NPY target.

Caenorhabditis elegans Heterochromatin protein 1 (HPL-2) links developmental plasticity, longevity and lipid metabolism

Background Heterochromatin protein 1 (HP1) family proteins have a well-characterized role in heterochromatin packaging and gene regulation. Their function in organismal development, however, is less well understood. Here we used genome-wide expression profiling to assess novel functions of the Caenorhabditis elegans HP1 homolog HPL-2 at specific developmental stages. Results We show that HPL-2 regulates the expression of germline genes, extracellular matrix components and genes involved in lipid metabolism. Comparison of our expression data with HPL-2 ChIP-on-chip profiles reveals that a significant number of genes up- and down-regulated in the absence of HPL-2 are bound by HPL-2. Germline genes are specifically up-regulated in hpl-2 mutants, consistent with the function of HPL-2 as a repressor of ectopic germ cell fate. In addition, microarray results and phenotypic analysis suggest that HPL-2 regulates the dauer developmental decision, a striking example of phenotypic plasticity in which environmental conditions determine developmental fate. HPL-2 acts in dauer at least partly through modulation of daf-2/IIS and TGF-β signaling pathways, major determinants of the dauer program. hpl-2 mutants also show increased longevity and altered lipid metabolism, hallmarks of the long-lived, stress resistant dauers. Conclusions Our results suggest that the worm HP1 homologue HPL-2 may coordinately regulate dauer diapause, longevity and lipid metabolism, three processes dependent on developmental input and environmental conditions. Our findings are of general interest as a paradigm of how chromatin factors can both stabilize development by buffering environmental variation, and guide the organism through remodeling events that require plasticity of cell fate regulation.

Continuous or repeated prolonged cisplatin infusions in children: a prospective study on ototoxicity, platinum concentrations, and standard serum parameters

BACKGROUND: To overcome the ototoxicity of cisplatin, single bolus infusions were replaced by repeated prolonged infusions of lower doses or by continuous infusions at still lower infusion rates. However, considering ototoxicity little is, in fact, known about the tolerance of repeated prolonged or continuous infusion in children. PROCEDURE: Auditory function was monitored along with plasma concentrations of free and total platinum (Pt), and with standard serum parameters (sodium, potassium, calcium, magnesium, phosphate, chloride, and creatinine) in 24 children receiving cisplatin by continuous infusion for the treatment of neuroblastoma and osteosarcoma or by repeated 1 or 6 hr infusions for the treatment of germ cell tumors. RESULTS: Hearing deteriorated in 10/15 osteosarcoma patients, 2/3 neuroblastoma patients, and 1/6 patients with germ cell tumors. Ototoxicity occurred after cumulative doses between 120 and 360 mg/m(2) cisplatin. In osteosarcoma patients, ototoxicity was associated with a comparatively higher mean plasma concentration of free Pt. However, Pt plasma concentrations did not discriminate between patients with or without ototoxicity. In patients experiencing ototoxicity serum creatinine increased by 45% compared to pre-treatment levels (mean). Serum creatinine increased by 26% in patients without ototoxicity (P < 0.05, Mann-Whitney Rank sum test). Despite standardized hydration, discrete but significant changes of potassium, sodium, magnesium, and phosphate were observed during and/or after cisplatin infusion, which, however, did not discriminate between patients with and without ototoxicity. CONCLUSIONS: While continuous cisplatin infusions are less nephrotoxic than repeated prolonged infusions, we observed considerable ototoxicity in patients treated with continuous cisplatin infusions, which necessitates further evaluations on the tolerance of continuous cisplatin infusions in children.

Does diagnostic delay result in decreased survival in paediatric brain tumours?

To study the hypothesis that a delay in the diagnosis of paediatric brain tumours results in decreased survival outcome probability, we compared the prediagnostic period of 315 brain tumour patients (median age 6.7 years, range, 0 to 16 years) with progression-free and overall survival. The median prediagnostic symptomatic interval was 60 days (range, 0 to 3,480 days), with a median parental delay of 14 days (range, 0 to 1,835 days) and a median doctor's delay of 14 days (range, 0 to 3,480 days). The prediagnostic symptomatic interval correlated significantly with the patient age, tumour histology, tumour location and year of diagnosis, but not with gender. We then grouped the patients according to histology (low-grade glioma [n=77], medulloblastoma [n=57], high-grade glioma [n=40], craniopharyngioma [n=27], ependymoma [n=20] and germ cell tumours [n=18]). Contrary to common belief, long prediagnostic symptomatic interval or long doctor's delay did not result in decreased survival outcome probability in any of these groups. The effect of tumour biology on survival seems to be dominant and overwhelms any possible opposing effect on survival of a delay in diagnosis.

Spinal cord injury causes sustained disruption of the blood-testis barrier in the rat.

There is a high incidence of infertility in males following traumatic spinal cord injury (SCI). Quality of semen is frequently poor in these patients, but the pathophysiological mechanism(s) causing this are not known. Blood-testis barrier (BTB) integrity following SCI has not previously been examined. The objective of this study was to characterize the effects of spinal contusion injury on the BTB in the rat. 63 adult, male Sprague Dawley rats received SCI (n = 28), laminectomy only (n = 7) or served as uninjured, age-matched controls (n = 28). Using dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), BTB permeability to the vascular contrast agent gadopentate dimeglumine (Gd) was assessed at either 72 hours-, or 10 months post-SCI. DCE-MRI data revealed that BTB permeability to Gd was greater than controls at both 72 h and 10 mo post-SCI. Histological evaluation of testis tissue showed increased BTB permeability to immunoglobulin G at both 72 hours- and 10 months post-SCI, compared to age-matched sham-operated and uninjured controls. Tight junctional integrity within the seminiferous epithelium was assessed; at 72 hours post-SCI, decreased expression of the tight junction protein occludin was observed. Presence of inflammation in the testes was also examined. High expression of the proinflammatory cytokine interleukin-1 beta was detected in testis tissue. CD68(+) immune cell infiltrate and mast cells were also detected within the seminiferous epithelium of both acute and chronic SCI groups but not in controls. In addition, extensive germ cell apoptosis was observed at 72 h post-SCI. Based on these results, we conclude that SCI is followed by compromised BTB integrity by as early as 72 hours post-injury in rats and is accompanied by a substantial immune response within the testis. Furthermore, our results indicate that the BTB remains compromised and testis immune cell infiltration persists for months after the initial injury.

Importance of the collagen adhesin ace in pathogenesis and protection against Enterococcus faecalis experimental endocarditis.

Ace is an adhesin to collagen from Enterococcus faecalis expressed conditionally after growth in serum or in the presence of collagen. Here, we generated an ace deletion mutant and showed that it was significantly attenuated versus wild-type OG1RF in a mixed infection rat endocarditis model (P<0.0001), while no differences were observed in a peritonitis model. Complemented OG1RFDeltaace (pAT392::ace) enhanced early (4 h) heart valve colonization versus OG1RFDeltaace (pAT392) (P = 0.0418), suggesting that Ace expression is important for early attachment. By flow cytometry using specific anti-recombinant Ace (rAce) immunoglobulins (Igs), we showed in vivo expression of Ace by OG1RF cells obtained directly from infected vegetations, consistent with our previous finding of anti-Ace antibodies in E. faecalis endocarditis patient sera. Finally, rats actively immunized against rAce were less susceptible to infection by OG1RF than non-immunized (P = 0.0004) or sham-immunized (P = 0.0475) by CFU counts. Similarly, animals given specific anti-rAce Igs were less likely to develop E. faecalis endocarditis (P = 0.0001) and showed fewer CFU in vegetations (P = 0.0146). In conclusion, we have shown for the first time that Ace is involved in pathogenesis of, and is useful for protection against, E. faecalis experimental endocarditis.

Estimation of male-to-female ratios of mutation rate in primates and rodents

Haldane (1935) developed a method for estimating the male-to-female ratio of mutation rate ($\alpha$) by using sex-linked recessive genetic disease, but in six different studies using hemophilia A data the estimates of $\alpha$ varied from 1.2 to 29.3. Direct genomic sequencing is a better approach, but it is laborious and not readily applicable to non-human organisms. To study the sex ratios of mutation rate in various mammals, I used an indirect method proposed by Miyata et al. (1987). This method takes advantage of the fact that different chromosomes segregate differently between males and females, and uses the ratios of mutation rate in sequences on different chromosomes to estimate the male-to-female ratio of mutation rate. I sequenced the last intron of ZFX and ZFY genes in 6 species of primates and 2 species of rodents; I also sequenced the partial genomic sequence of the Ube1x and Ube1y genes of mice and rats. The purposes of my study in addition to estimation of $\alpha$'s in different mammalian species, are to test the hypothesis that most mutations are replication dependent and to examine the generation-time effect on $\alpha$. The $\alpha$ value estimated from the ZFX and ZFY introns of the six primate specise is ${\sim}$6. This estimate is the same as an earlier estimate using only 4 species of primates, but the 95% confidence interval has been reduced from (2, 84) to (2, 33). The estimate of $\alpha$ in the rodents obtained from Zfx and Zfy introns is ${\sim}$1.9, and that deriving from Ube1x and Ube1y introns is ${\sim}$2. Both estimates have a 95% confidence interval from 1 to 3. These two estimates are very close to each other, but are only one-third of that of the primates, suggesting a generation-time effect on $\alpha$. An $\alpha$ of 6 in primates and 2 in rodents are close to the estimates of the male-to-female ratio of the number of germ-cell divisions per generation in humans and mice, which are 6 and 2, respectively, assuming the generation time in humans is 20 years and that in mice is 5 months. These findings suggest that errors during germ-cell DNA replication are the primary source of mutation and that $\alpha$ decreases with decreasing length of generation time. ^

Cisplatin Nephrotoxicity and Longitudinal Growth in Children With Solid Tumors: A Retrospective Cohort Study

Cisplatin, a major antineoplastic drug used in the treatment of solid tumors, is a known nephrotoxin. This retrospective cohort study evaluated the prevalence and severity of cisplatin nephrotoxicity in 54 children and its impact on height and weight.We recorded the weight, height, serum creatinine, and electrolytes in each cisplatin cycle and after 12 months of treatment. Nephrotoxicity was graded as follows: normal renal function (Grade 0); asymptomatic electrolyte disorders, including an increase in serum creatinine, up to 1.5 times baseline value (Grade 1); need for electrolyte supplementation <3 months and/or increase in serum creatinine 1.5 to 1.9 times from baseline (Grade 2); increase in serum creatinine 2 to 2.9 times from baseline or need for electrolyte supplementation for more than 3 months after treatment completion (Grade 3); and increase in serum creatinine ≥3 times from baseline or renal replacement therapy (Grade 4).Nephrotoxicity was observed in 41 subjects (75.9%). Grade 1 nephrotoxicity was observed in 18 patients (33.3%), Grade 2 in 5 patients (9.2%), and Grade 3 in 18 patients (33.3%). None had Grade 4 nephrotoxicity. Nephrotoxicity patients were younger and received higher cisplatin dose, they also had impairment in longitudinal growth manifested as statistically significant worsening on the height Z Score at 12 months after treatment. We used a multiple logistic regression model using the delta of height Z Score (baseline-12 months) as dependent variable in order to adjust for the main confounder variables such as: germ cell tumor, cisplatin total dose, serum magnesium levels at 12 months, gender, and nephrotoxicity grade. Patients with nephrotoxicity Grade 1 where at higher risk of not growing (OR 5.1, 95% CI 1.07-24.3, P=0.04). The cisplatin total dose had a significant negative relationship with magnesium levels at 12 months (Spearman r=-0.527, P=<0.001).

Esx1 dosage impacts reproductive fitness: Effects on viability and fertility

Numerous genes expressed in placenta or testis localize to the X-chromosome. Both tissues undergo specialized X-chromosome inactivation (imprinted paternal inactivation in placenta and MSCI in testicular germ cells). When the X-chromosome is duplicated or improperly inactivated, defects in placentation, growth and spermatogenesis are noted, suggesting tight control of X-chromosome gene dosage is important for reproduction. ^ Esx1 is a mouse homeobox gene on the X-chromosome with expression limited to extraembryonic tissues and testicular germ cells. Here, we examine the effects of increased and decreased Esx1 dosage on placental and testicular development, the role of genetic background on Esx1 function and characterize the human orthologue of Esx1. ^ Previously, by targeted deletion, Esx1 was shown to be an X-chromosome imprinted regulator of placental development and fetal growth. We show C57Bl6-congenic Esx1 mutants display a more severe phenotype with decreased viability and that the 129 genetic background contains dominant modifier genes that enhance Esx1 mutant survival. ^ Varying Esx1 dosage impacts testicular germ cell development. Esx1 hemizygous null mice are fertile, but we show their testes are two-thirds normal size. To examine the effect of increased Esx1 dosage, Esx1 BAC transgenic mice were generated. Increased Esx1 dosage results in dramatic deficits in testicular germ cell development, leading to sterility and testes one-fourth normal size. We show germ cell loss occurs through apoptosis, begins between postnatal day 6 and 10, and that no spermatocytes complete meiosis. Interestingly, increased Esx1 dosage in testes mimics germ cell loss seen in Klinefelter's (XXY) mice and humans and may represent a molecular mechanism for the infertility characteristic of this syndrome. ^ Esx1 dosage impacts reproductive fitness when maternally transmitted. Three transgenic founder females were unable to transmit the transgene to live offspring, but did produce transgenic pups at earlier stages. Additionally, one line of Esx1 BAC transgenic mice demonstrated decreased embryo size and fitness when the transgene is inherited compared to wild type littermates. ^ It is possible that Esx1 plays a role in human disorders of pregnancy, growth and spermatogenesis. Therefore, we cloned and characterized ESX1L (human Esx1), and show it is expressed in human testis and placenta. ^

Identifying the roles of the Escherichia coli FtsZ-associated proteins by minimizing the requirements for division

Formation of the FtsZ ring (Z ring) in Escherichia coli is the first step in assembly of the divisome, a molecular machine composed of 14 known proteins which are all required for cell division. Although the biochemical functions of most divisome proteins are unknown, several of these have overlapping roles in ensuring that the Z ring assembles at the cytoplasmic membrane and is active. ^ We identified a single amino acid change in FtsA, R286W, renamed FtsA*, that completely bypasses the requirement for ZipA in cell division. This and other data suggest that FtsA* is a hyperactive form of FtsA that can replace the multiple functions normally assumed by ZipA, which include stabilization of Z rings, recruitment of downstream cell division proteins, and anchoring the Z ring to the membrane. This is the first example of complete functional replacement of an essential prokaryotic cell division protein by another. ^ Cells expressing ftsA* with a complete deletion of ftsK are viable and divide, although many of these ftsK null cells formed multiseptate chains, suggesting a role in cell separation for FtsK. In addition, strains expressing extra ftsAZ, ftsQ, ftsB, zipA or ftsN, were also able to survive and divide in the absence of ftsK. The cytoplasmic and transmembrane domains of FtsQ were sufficient to allow viability and septum formation to ftsK deleted strains. These findings suggest that FtsK is normally involved in stabilizing the divisome and shares functional overlap with other cell division proteins. ^ As well as permitting the removal of other divisome components, the presence of FtsA* in otherwise wild-type cells accelerated Z-ring assembly, which resulted in a significant decrease in the average length of cells. In support of its role in Z-ring stability, FtsA* suppressed the cell division inhibition caused by overexpressing FtsZ. FtsA* did not affect FtsZ turnover within the Z ring as measured by fluorescence recovery after photobleaching. Turnover of FtsA* in the ring was somewhat faster than wild-type FtsA. Yeast two-hybrid data suggest that FtsA* has an increased affinity for FtsZ relative to wild-type FtsA. These results indicate that FtsA* interacts with FtsZ more strongly, and its enhancement of Z ring assembly may explain why FtsA* can permit survival of cells lacking ZipA or FtsK.^

Caenorhabditis elegans germinal center kinase (Gck-1) is a p-body component that inhibits precocious ectopic MAP kinase dependent meiotic maturation

The Caenorhabditis elegans germline is an excellent model system for studying meiosis, as the gonad contains germ cells in all stages of meiosis I prophase in a linear temporal and spatial pattern. To form healthy gametes, many events must be coordinated. Failure of any step in the process can reduce fertility. Here, we describe a C. elegans Germinal Center Kinase, GCK-1, that is essential for the accurate progression of germ cells through meiosis I prophase. In the absence of GCK-1, germ cells undergo precocious maturation due to the activation of a specific MAP kinase isoform. Furthermore, GCK-1 localizes to P-bodies, RNP particles that have been implicated in RNA degradation and translational control. Like two other components of C. elegans germline P-bodies, GCK-1 functions to limit physiological germ cell apoptosis. This is the first study to identify a role for a GCK-III kinase in metazoan germ cell development and to link P-body function with MAP kinase activation and germ cell maturation. ^

Downstream targets of the Rhox5 homeobox gene

The X-linked mouse Rhox gene cluster contains over 30 homeobox genes that are candidates to regulate multiple steps in male and female gametogenesis. The founding member of the Rhox gene cluster, Rhox5, is an androgen-dependent gene expressed in Sertoli cells that promotes the survival and differentiation of the adjacent male germ cells. To decipher downstream signaling pathways of Rhox5, I used in vivo and in vitro microarray profiling to identify and characterize downstream targets of Rhox5 in the testis. This led to the identification of many Rhox5 -regulated genes, two of which I focused on in more detail. One of them, Unc5c, encodes a pro-apoptotic receptor with tumor suppressor activity that I found is negatively regulated by Rhox5 through a Rhox5-response element in the Unc5c 5' untranslated region (5' UTR). Examination of other mouse Rhox family members revealed that Rhox2 and Rhox3 also have the ability to downregulate Unc5c expression. The human RHOX protein RHOXF2 also had this ability, indicating that Unc5c repression is a conserved Rhox-dependent response. The repression of Unc5c expression by Rhox5 may, in part, mediate Rhox5's pro-survival function in the testis, as I found that Unc5c mutant mice have decreased germ cell apoptosis in the testis. This along with my other data leads me to propose a model in which Rhox5 is a negative regulator upstream of Unc5c in a Sertoli-cell pathway that promotes germ-cell survival. The other Rhox5-regulated gene that I studied in detail is insulin II (Ins2). Several lines of evidence, including electrophoretic mobility shift anaylsis, promoter mutagenesis, and chromatin immuoprecipitation analysis indicated that Ins2 is a direct target of Rhox5. Structure-function analysis identified homeodomain residues and the RHOX5 amino-terminal domain crucial for conferring Ins2 inducibility. Rhox5 regulates not only the Ins2 gene but also genes encoding other secreted proteins regulating metabolism (adiponectin and resistin), the rate-liming enzyme for monosaturated fatty acid biosynthesis (SCD-1), and transcription factors crucial for regulating metabolism (the nuclear hormone receptor PPARγ). I propose that the regulation of some or all of these molecules in Sertoli cells is responsible for the Rhox5-dependent survival of the adjacent germ cells. ^

IDENTIFICATION AND ANALYSIS OF A NOVEL ROLE FOR THE TOUSLED-LIKE KINASE IN REGULATING MITOTIC SPINDLE DYNAMICS

Deregulation of kinase activity is one example of how cells become cancerous by evading evolutionary constraints. The Tousled kinase (Tsl) was initially identified in Arabidopsis thaliana as a developmentally important kinase. There are two mammalian orthologues of Tsl and one orthologue in C. elegans, TLK-1, which is essential for embryonic viability and germ cell development. Depletion of TLK-1 leads to embryonic arrest large, distended nuclei, and ultimately embryonic lethality. Prior to terminal arrest, TLK-1-depleted embryos undergo aberrant mitoses characterized by poor metaphase chromosome alignment, delayed mitotic progression, lagging chromosomes, and supernumerary centrosomes. I discovered an unanticipated requirement for TLK-1 in mitotic spindle assembly and positioning. Normally, in the newly-fertilized zygote (P0) the maternal pronucleus migrates toward the paternal pronucleus at the posterior end of the embryo. After pronuclear meeting, the pronuclear-centrosome complex rotates 90° during centration to align on the anteroposterior axis followed by nuclear envelope breakdown (NEBD). However, in TLK-1-depleted P0 embryos, the centrosome-pronuclear complex rotation is significantly delayed with respect to NEBD and chromosome congression, Additionally, centrosome positions over time in tlk-1(RNAi) early embryos revealed a defect in posterior centrosome positioning during spindle-pronuclear centration, and 4D analysis of centrosome positions and movement in newly fertilized embryos showed aberrant centrosome dynamics in TLK-1-depleted embryos. Several mechanisms contribute to spindle rotation, one of which is the anchoring of astral microtubules to the cell cortex. Attachment of these microtubules to the cortices is thought to confer the necessary stability and forces in order to rotate the centrosome-pronuclear complex in a timely fashion. Analysis of a microtubule end-binding protein revealed that TLK-1-depleted embryos exhibit a more stochastic distribution of microtubule growth toward the cell cortices, and the types of microtubule attachments appear to differ from wild-type embryos. Additionally, fewer astral microtubules are in the vicinity of the cell cortex, thus suggesting that the delayed spindle rotation could be in part due to a lack of appropriate microtubule attachments to the cell cortex. Together with recently published biochemical data revealing the Tousled-like kinases associate with components of the dynein microtubule motor complex in humans, these data suggest that Tousled-like kinases play an important role in mitotic spindle assembly and positioning.

Expression and function of $\beta$-1,4-galactosyltransferase during wild-type and T/{\it t\/} -mutant spermatogenesis

In the mouse, gamete recognition is mediated in part by the binding of sperm surface $\beta$1,4 galactosyltransferase (GalTase) to specific oligosaccharide residues on the zona pellucida ZP3. The expression of GalTase on the sperm surface is regulated by alleles within the distal segment of the T/t complex and results in a haploid-specific increase in GalTase expression on spermatids and sperm from t-bearing males, suggesting that differences in sperm GalTase activity may contribute to t-sperm transmission ratio distortion. In this study, the expression of GalTase RNA during wild-type and T/t-mutant spermatogenesis was characterized and the role of GalTase was analyzed in transmission ratio distortion. It was found that spermatogenic cells predominantly express the long form of the GalTase RNA, which encodes the GalTase protein that is preferentially targeted to the cell surface in somatic cells. In wild-type testes, GalTase RNA accumulates during the maturation of primary spermatocytes, reaches peak levels prior to meiosis, and decreases and meiosis. GalTase RNA accumulates to similar levels during the maturation of +/t and t/t primary spermatocytes, but unlike wild-type, the level of GalTase RNA in t-spermatocytes remains elevated during meiotic division. Consequently, spermatids in t-mutant testes inherit higher levels of GalTase RNA than do wild-type spermatids, which likely accounts for the haploid-specific increase in surface GalTase activity characteristic of spermatids from t-bearing mice.^ The functional significance of the increased GalTase activity during t-sperm transmission ratio distortion was determined by examining the distribution of GalTase RNA and surface GalTase protein in haploid spermatids from +/t males. Results show that +- and t-spermatids have similar levels of both GalTase RNA and protein, indicating that transmission ratio distortion in +/t mice is not likely due to haploid-specific differences in sperm surface GalTase activity.^ The presence of GalTase on the surface of an early spermatogenic cells before it is required on the mature sperm to perform its function during gamete binding suggests a separate function for GalTase in Sertoli-germ cell adhesion. Studies indicate that cell surface GalTase partly mediates the initial adhesion of pachytene spermatocytes, but not haploid spermatids, to Sertoli cells. ^

Reduced fertility in mice deficient for the POU protein sperm-1

Members of the POU-homeodomain gene family encode transcriptional regulatory molecules that play important roles in terminal differentiation of many organ systems. Sperm-1 (Sprm-1) is a POU domain factor that is exclusively expressed in the differentiating male germ cell. We show here that the Sprm-1 protein is expressed in the haploid spermatid and that 129/Sv Sprm-1(−/−) mice are subfertile when compared with wild-type or heterozygous littermates yet exhibit normal testicular morphology and produce normal numbers of mobile spermatozoa. Our data suggest that the Sprm-1 protein plays a discrete regulatory function in the haploid spermatid, which is required for the optimal function, but not the terminal differentiation, of the male germ cell.