Determination of mitochondrial genetic diversity in mammals

Mitochondrial DNA (mtDNA) is one of the most Popular population genetic markers. Its relevance as an indicator Of Population size and history has recently been questioned by several large-scale studies in animals reporting evidence for recurrent adaptive evolution, at least in invertebrates. Here we focus on mammals, a more restricted taxonomic group for which the issue of mtDNA near neutrality is crucial. By analyzing the distribution of mtDNA diversity across species and relating 4 to allozyme diversity, life-history traits, and taxonomy, we show that (i) mtDNA in mammals (toes not reject the nearly neutral model; (ii) mtDNA diversity, however, is unrelated to any of the 14 life-history and ecological variables that we analyzed, including body mass, geographic range, and The World Conservation Union (IUCN) categorization; (iii) mtDNA diversity is highly variable between mammalian orders and families; (iv) this taxonomic effect is most likely explained by variations of mutation rate between lineages. These results are indicative of a strong stochasticity of effective population size in mammalian species. They Suggest that, even in the absence of selection, mtDNA genetic diversity is essentially unpredictable, knowing species biology, and probably uncorrelated to species abundance.

Amphioxus molecular biology: insights into vertebrate evolution and developmental mechanisms

The cephalochordate amphioxus is the best available proxy for the last common invertebrate ancestor of the vertebrates. During the last decade, the developmental genetics of amphioxus have been extensively examined for insights into the evolutionary origin and early evolution of the vertebrates. Comparisons between expression domains of homologous genes in amphioxus and vertebrates have strengthened proposed homologies between specific body parts. Molecular genetic studies have also highlighted parallels in the developmental mechanisms of amphioxus and vertebrates. In both groups, a similar nested pattern of Hox gene expression is involved in rostrocaudal patterning of the neural tube, and homologous genes also appear to be involved in dorsoventral neural patterning. Studies of amphioxus molecular biology have also hinted that the protochordate ancestor of the vertebrates included cell populations that modified their developmental genetic pathways during early vertebrate evolution to yield definitive neural crest and neurogenic placodes. We also discuss how the application of expressed sequence tag and gene-mapping approaches to amphioxus have combined with developmental studies to advance our understanding of chordate genome evolution. We conclude by considering the potential offered by the sequencing of the amphioxus genome, which was completed in late 2004.

Evolutionary developmental biology: impact on systematic theory and practice, and the contribution of systematics

Evolutionary developmental genetics brings together systematists, morphologists and developmental geneticists; it will therefore impact on each of these component disciplines. The goals and methods of phylogenetic analysis are reviewed here, and the contribution of evolutionary developmental genetics to morphological systematics, in terms of character conceptualisation and primary homology assessment, is discussed. Evolutionary developmental genetics, like its component disciplines phylogenetic systematics and comparative morphology, is concerned with homology concepts. Phylogenetic concepts of homology and their limitations are considered here, and the need for independent homology statements at different levels of biological organisation is evaluated. The role of systematics in evolutionary developmental genetics is outlined. Phylogenetic systematics and comparative morphology will suggest effective sampling strategies to developmental geneticists. Phylogenetic systematics provides hypotheses of character evolution (including parallel evolution and convergence), stimulating investigations into the evolutionary gains and losses of morphologies. Comparative morphology identifies those structures that are not easily amenable to typological categorisation, and that may be of particular interest in terms of developmental genetics. The concepts of latent homology and genetic recall may also prove useful in the evolutionary interpretation of developmental genetic data.

Sex chromosome evolution in fish: the formation of the neo-Y chromosome in Eigenmannia (Gymnotiformes)

Chromosomes of a species of Eigenmannia presenting a X1X1X2X2:X1X2Y sex chromosome system, resulting from a Y-autosome Robertsonian translocation, were analyzed using the C-banding technique, chromomycin A(3) (CMA(3)) and mithramycin (MM) staining and in situ digestion by the restriction endonuclease AluI. A comparison of the metacentric Y chromosome of males with the corresponding acrocentrics in females indicated that a C-band-positive, CMA(3)/MM-fluorescent and AluI digestion-resistant region had been lost during the process of translocation, resulting in a diminution of heterochromatin in the males. It is hypothesized that the presence of a smaller amount of G+C-rich heterochromatin in the sex chromosomes of the heteromorphic sex when compared with the homomorphic sex may be associated with the sex determination mechanism in this species and may be a more widely occurring phenomenon in fish with differentiated sex chromosomes than was initially thought.

Reproductive cycle and recruitment period of Ocypode quadrata (Decapoda, Ocypodidae) at a sandy beach in southeastern Brazil

The reproductive cycle and recruitment period of a ghost crab population from Ubatuba, São Paulo, Brazil were investigated by means of examining the developmental stages of gonads of breeding crabs and the ingress of young recruits to the studied population. Monthly collections over a one-year period were carried out during nocturnal low-tide periods at Vermelha beach. The morphology of the abdomen and pleopods was used for sex determination. All captured crabs were measured for carapace width and dissected for the determination of the development stage of the gonads. A total of 582 specimens was captured: 271 males, 241 females, and 70 juveniles. Size ranged from 8.5 to 37.5 mm for males, from 9.5 to 39.2 mm for females, and from 5.8 to 12 mm for early juveniles. Median size of males and females did not differ statistically. The frequency of ovigerous females was markedly low. The onset of sexual maturity in females is achieved at around 23 mm of carapace width. Mature females with advanced gonad stages were not recorded from May to September. Recruitment of young was highest during summer, but the presence of early and late juvenile specimens throughout the year indicates that continuous recruitment is taking place in the studied population.

Karyotype characterization, constitutive heterochromatin and nucleolus organizer regions of Paranaita opima (Coleoptera, Chrysomelidae, Alticinae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Chromosome analysis in Pseudopaludicola (Anura, Leiuperidae), with description of sex chromosomes XX/XY in P-saltica

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Study of chromosomal and nucleolar aspects in testes of Nysius californicus (Heteroptera: Lygaeidae)

In Nysius californicus (family Lygaeidae, subfamily Orsillinae), a pest commonly known as the seed bug, the chromosome complement is 2n = 16 (12A + 2m + XY), testes are formed by seven seminiferous tubules covered by an orange-colored membrane, and spermatogenesis is cystic. At prophase, sex chromosomes are heteropycnotic and autosomes usually show a chiasma. At metaphase, sex chromosomes along with microchromosomes may be seen located at the center of a ring formed by the remaining autosomes. A characteristic specific of N. californicus was the presence of nucleolar material observed from the cystic cell to the completely differentiated spermatozoon. Variations in size, shape and location of the nucleolar material occur during this process, denoting a variable degree of activity in the different stages. ©FUNPEC-RP.

Morphology, sex ratio and gene expression of Day 14 in vivo and in vitro bovine embryos

The present study was designed to compare Day 14 bovine embryos that were produced entirely in vitro using the post-hatching development (PHD) system with in vivo-derived embryos without or with transient PHD culture from Day 7 to Day 14. Embryos on Day 14 were used for sex determination and gene expression analysis of PLAC8, KRT8, CD9, SLC2A1, SLC2A3, PGK1, HSF1, MNSOD, HSP70 and IFNT using real-time quantitative (q) polymerase chain reaction (PCR). First, Day 7 in vivo-and in vitro-produced embryos were subjected to the PHD system. A higher rate of survival was observed for in vitro embryos on Day 14. Comparing Day 14 embryos produced completely in vivo or completely in vitro revealed that the mean size of the former group was greater than that of the latter (10.29±1.83 vs 2.68±0.33mm, respectively). Expression of the HSP70 and SLC2A1 genes was down-and upregulated, respectively, in the in vitro embryos. The present study shows that in vitro embryos cultured in the PHD system are smaller than in vivo embryos and that of the 10 genes analysed, only two were differentially expressed between the two groups. These findings indicate that, owing to the poor survival rate, the PHD system is not reliable for evaluation of in vitro embryo quality. © 2013 CSIRO.

The karyotype of Alouatta fusca clamitans from Rio de Janeiro, Brazil: Evidence for a y-autosome translocation

Os cariótipos referentes a quatro machos de Alouatta fusca clamitans oriundos do Rio de Janeiro foram analisados através de técnicas de bandamento G, C e NOR. O número diplóide em todos os espécimes foi igual a 49, com a presença de três cromossomos não pareados. A comparação dos padrões de bandamento G com espécimes previamente descritos com 2n = 50 revelou a ocorrência de uma translocação do tipo Y-autossomo, modificando o sistema cromossômico de determinação sexual para o tipo múltiplo, X1X2Y/X1X1 X2X2. Os blocos de heterocromatina constitutiva se distribuíram na região pericentromérica de todos os cromossomos; segmentos intercalares e teloméricos foram visualizados em um par acrocêntrico e em outro submetacêntrico, respectivamente. As regiões organizadoras de nucléolo se localizaram no braço longo de dois pares de pequenos acrocêntricos.

Diversidade cariotípica e molecular de Leptodactylus (Anura, Leptodactylidae) e obtenção de sondas cromossomo-específicas de anfíbio por citometria de fluxo

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Absence of inactivating mutations and deletions in the DMRT1 and FGF9 genes in a large cohort of 46,XY patients with gonadal dysgenesis

Despite advances in our understanding of the mechanisms involved in sex determination and differentiation, the specific roles of many genes in these processes are not completely understood in humans. Both DMRT1 and FGF9 are among this group of genes. Dmrt1 controls germ cell differentiation, proliferation, migration and pluripotency and Sertoli cell proliferation and differentiation. Fgf9 has been considered a critical factor in early testicular development and germ cell survival in mice. We screened for the presence of DMRT1 and FGF9 mutations in 33 patients with 46,XY gonadal dysgenesis. No deletions in either DMRT1 or FGF9 were identified using the MLPA technique. Eight allelic variants of DMRT1 were identified, and in silico analysis suggested that the novel c.968-15insTTCTCTCT variant and the c.774G>C (rs146975077) variant could have potentially deleterious effects on the DMRT1 protein. Nine previously described FGF9 allelic variants and six different alleles of the 3' UTR microsatellite were identified. However, none of these DMRT1 or FGF9 variants was associated with increased 46,XY gonadal dysgenesis. In conclusion, our study suggests that neither DMRT1 nor FGF9 abnormalities are frequently involved in dysgenetic male gonad development in patients with non-syndromic 46,XY disorder of sex development. (C) 2012 Published by Elsevier Masson SAS.

The clinical impact of chromosomal rearrangements with breakpoints upstream of the SOX9 gene: two novel de novo balanced translocations associated with acampomelic campomelic dysplasia

Abstract Background The association of balanced rearrangements with breakpoints near SOX9 [SRY (sex determining region Y)-box 9] with skeletal abnormalities has been ascribed to the presumptive altering of SOX9 expression by the direct disruption of regulatory elements, their separation from SOX9 or the effect of juxtaposed sequences. Case presentation We report on two sporadic apparently balanced translocations, t(7;17)(p13;q24) and t(17;20)(q24.3;q11.2), whose carriers have skeletal abnormalities that led to the diagnosis of acampomelic campomelic dysplasia (ACD; MIM 114290). No pathogenic chromosomal imbalances were detected by a-CGH. The chromosome 17 breakpoints were mapped, respectively, 917–855 kb and 601–585 kb upstream of the SOX9 gene. A distal cluster of balanced rearrangements breakpoints on chromosome 17 associated with SOX9-related skeletal disorders has been mapped to a segment 932–789 kb upstream of SOX9. In this cluster, the breakpoint of the herein described t(17;20) is the most telomeric to SOX9, thus allowing the redefining of the telomeric boundary of the distal breakpoint cluster region related to skeletal disorders to 601–585 kb upstream of SOX9. Although both patients have skeletal abnormalities, the t(7;17) carrier presents with relatively mild clinical features, whereas the t(17;20) was detected in a boy with severe broncheomalacia, depending on mechanical ventilation. Balanced and unbalanced rearrangements associated with disorders of sex determination led to the mapping of a regulatory region of SOX9 function on testicular differentiation to a 517–595 kb interval upstream of SOX9, in addition to TESCO (Testis-specific enhancer of SOX9 core). As the carrier of t(17;20) has an XY sex-chromosome constitution and normal male development for his age, the segment of chromosome 17 distal to the translocation breakpoint should contain the regulatory elements for normal testis development. Conclusions These two novel translocations illustrate the clinical variability in carriers of balanced translocations with breakpoints near SOX9. The translocation t(17;20) breakpoint provides further evidence for an additional testis-specific SOX9 enhancer 517 to 595 kb upstream of the SOX9 gene.

No evidence of predation causing female-biased sex ratios in marine pelagic copepods

Although sex ratios close to unity are expected in dioecious species, biased sex ratios are common in nature. It is essential to understand causes of skewed sex ratios in situ, as they can lead to mate limitation and have implications for the success of natural populations. Female-skewed sex ratios are commonly observed in copepods in situ. Here we discuss the challenges of copepod sex ratio research and provide a critical review of factors determining copepod sex ratios, focusing on 2 main objectives. The first is a critique of the male predation theory, which is currently the main process thought to be responsible for female-skewed sex ratios. It assumes that males have higher mortality because of increased vulnerability to predation during their search for mates. We show that there is little support for the male predation theory, that sex ratios skewed toward females occur in the absence of predation, that sex ratios are not related to predation pressure, and that where sex-skewed predation does occur, it is biased toward females. Our second objective is to suggest alternative hypotheses regarding the determination of sex ratios. We demonstrate that environmental factors, environmental sex determination and sex change have strong effects on copepod sex ratios, and suggest that differential physiological longevity of males and females may be more important in determining sex ratios than previously thought. We suggest that copepod sex ratios are the result of a mixture of factors.