Maternal effect on salinity tolerance during germination of Ricinus communis

p.93-101

The Caenorhabditis elegans maternal-effect sterile proteins, MES-2, MES-3, and MES-6, are associated in a complex in embryos

The Caenorhabditis elegans maternal-effect sterile genes, mes-2, mes-3, mes-4, and mes-6, encode nuclear proteins that are essential for germ-line development. They are thought to be involved in a common process because their mutant phenotypes are similar. MES-2 and MES-6 are homologs of Enhancer of zeste and extra sex combs, both members of the Polycomb group of chromatin regulators in insects and vertebrates. MES-3 is a novel protein, and MES-4 is a SET-domain protein. To investigate whether the MES proteins interact and likely function as a complex, we performed biochemical analyses on C. elegans embryo extracts. Results of immunoprecipitation experiments indicate that MES-2, MES-3, and MES-6 are associated in a complex and that MES-4 is not associated with this complex. Based on in vitro binding assays, MES-2 and MES-6 interact directly, via the amino terminal portion of MES-2. Sucrose density gradient fractionation and gel filtration chromatography were performed to determine the Stokes radius and sedimentation coefficient of the MES-2/MES-3/MES-6 complex. Based on those two values, we estimate that the molecular mass of the complex is ≈255 kDa, close to the sum of the three known components. Our results suggest that the two C. elegans Polycomb group homologs (MES-2 and MES-6) associate with a novel partner (MES-3) to regulate germ-line development in C. elegans.

X-Linked Retinitis Pigmentosa 2 Is a Novel Maternal-Effect Gene Required for Left-Right Asymmetry in Zebrafish

Retinitis pigmentosa 2 (RP2) gene is responsible for up to 20% of X-linked retinitis pigmentosa, a severe heterogeneous genetic disorder resulting in progressive retinal degeneration in humans. In vertebrates, several bodies of evidence have clearly established the role of Rp2 protein in cilia genesis and/or function. Unexpectedly, some observations in zebrafish have suggested the oocyte-predominant expression of the rp2 gene, a typical feature of maternal-effect genes. In the present study, we investigate the maternal inheritance of rp2 gene products in zebrafish eggs in order to address whether rp2 could be a novel maternal-effect gene required for normal development. Although both rp2 mRNA and corresponding protein are expressed during oogenesis, rp2 mRNA is maternally inherited, in contrast to Rp2 protein. A knockdown of the protein transcribed from both rp2 maternal and zygotic mRNA results in delayed epiboly and severe developmental defects, including eye malformations, that were not observed when only the protein from zygotic origin was knocked down. Moreover, the knockdown of maternal and zygotic Rp2 revealed a high incidence of left-right asymmetry establishment defects compared to only zygotic knockdown. Here we show that rp2 is a novel maternal-effect gene exclusively expressed in oocytes within the zebrafish ovary and demonstrate that maternal rp2 mRNA is essential for successful embryonic development and thus contributes to egg developmental competence. Our observations also reveal that Rp2 protein translated from maternal mRNA is important to allow normal heart loop formation, thus providing evidence of a direct maternal contribution to left-right asymmetry establishment.

Consequences of maternal yolk testosterone for offspring development and survival : experimental test in a lizard

1. Hormone-mediated maternal effects and developmental plasticity are important sources of phenotypic variation, with potential consequences for trait evolution. Yet our understanding of the importance of maternal hormones for offspring fitness in natural populations is very limited, particularly in non-avian species.

2. We experimentally elevated yolk testosterone by injection of a physiological dose into eggs of the lizard Ctenophorus fordi Storr, to investigate its roles in offspring development, growth and survival.

3. Yolk testosterone did not influence incubation period, basic hatchling morphology or survival under natural conditions. However, there was evidence for increased growth in hatchlings from testosterone-treated eggs, suggesting that maternal hormones have potential fitness consequences in natural populations.

4. The positive effect of prenatal testosterone exposure on postnatal growth could represent a taxonomically widespread developmental mechanism that has evolved into an adaptive maternal effect in some taxa, but remains deleterious or selectively neutral in others.

5. A broader taxonomic perspective should increase our understanding of the role of physiological constraints in the evolution of endocrine maternal effects.

Single early prenatal lipopolysaccharide exposure impairs striatal monoamines and maternal care in female rats

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

Maternal effects and the evolution of aposematic signals

Aposematic signals that warn predators of the noxious qualities of prey gain their greatest selective advantage when predators have already experienced similar signals. Existing theory explains how such signals can spread through selective advantage after they are present at some critical frequency, but is unclear about how warning signals can be selectively advantageous when the trait is initially rare (i.e., when it first arises through mutation) and predators are naive. When aposematism is controlled by a maternal effect gene, the difficulty of initial rarity may be overcome. Unlike a zygotically expressed gene, a maternally expressed aposematism gene will be hidden from selection because it is not phenotypically expressed in the first individual with the mutation. Furthermore, the first individual carrying the new mutation will produce an entire family of aposematic offspring, thereby providing an immediate fitness advantage to this gene.

Further evidence for a parent-of-origin effect at the NOP9 locus on language-related phenotypes

Background - Specific language impairment (SLI) is a common neurodevelopmental disorder, observed in 5–10 % of children. Family and twin studies suggest a strong genetic component, but relatively few candidate genes have been reported to date. A recent genome-wide association study (GWAS) described the first statistically significant association specifically for a SLI cohort between a missense variant (rs4280164) in the NOP9 gene and language-related phenotypes under a parent-of-origin model. Replications of these findings are particularly challenging because the availability of parental DNA is required. Methods - We used two independent family-based cohorts characterised with reading- and language-related traits: a longitudinal cohort (n = 106 informative families) including children with language and reading difficulties and a nuclear family cohort (n = 264 families) selected for dyslexia. Results - We observed association with language-related measures when modelling for parent-of-origin effects at the NOP9 locus in both cohorts: minimum P = 0.001 for phonological awareness with a paternal effect in the first cohort and minimum P = 0.0004 for irregular word reading with a maternal effect in the second cohort. Allelic and parental trends were not consistent when compared to the original study. Conclusions - A parent-of-origin effect at this locus was detected in both cohorts, albeit with different trends. These findings contribute in interpreting the original GWAS report and support further investigations of the NOP9 locus and its role in language-related traits. A systematic evaluation of parent-of-origin effects in genetic association studies has the potential to reveal novel mechanisms underlying complex traits.

Causes and consequences of variation in nestling immune function

Defence against pathogens is a vital need of all living organisms that has led to the evolution of complex immune mechanisms. However, although immunocompetence the ability to resist pathogens and control infection has in recent decades become a focus for research in evolutionary ecology, the variation in immune function observed in natural populations is relatively little understood. This thesis examines sources of this variation (environmental, genetic and maternal effects) during the nestling stage and its fitness consequences in wild populations of passerines: the blue tit (Cyanistes caeruleus) and the collared flycatcher (Ficedula albicollis). A developing organism may face a dilemma as to whether to allocate limited resources to growth or to immune defences. The optimal level of investment in immunity is shaped inherently by specific requirements of the environment. If the probability of contracting infection is low, maintaining high growth rates even at the expense of immune function may be advantageous for nestlings, as body mass is usually a good predictor of post-fledging survival. In experiments with blue tits and haematophagous hen fleas (Ceratophyllus gallinae) using two methods, methionine supplementation (to manipulate nestlings resource allocation to cellular immune function) and food supplementation (to increase resource availability), I confirmed that there is a trade-off between growth and immunity and that the abundance of ectoparasites is an environmental factor affecting allocation of resources to immune function. A cross-fostering experiment also revealed that environmental heterogeneity in terms of abundance of ectoparasites may contribute to maintaining additive genetic variation in immunity and other traits. Animal model analysis of extensive data collected from the population of collared flycatchers on Gotland (Sweden) allowed examination of the narrow-sense heritability of PHA-response the most commonly used index of cellular immunocompetence in avian studies. PHA-response is not heritable in this population, but is subject to a non-heritable origin (presumably maternal) effect. However, experimental manipulation of yolk androgen levels indicates that the mechanism of the maternal effect in PHA-response is not in ovo deposition of androgens. The relationship between PHA-response and recruitment was studied for over 1300 collared flycatcher nestlings. Multivariate selection analysis shows that it is body mass, not PHA-response, that is under direct selection. PHA-response appears to be related to recruitment because of its positive relationship with body mass. These results imply that either PHA-response fails to capture the immune mechanisms that are relevant for defence against pathogens encountered by fledglings or that the selection pressure from parasites is not as strong as commonly assumed.

Growth and survival of reciprocal crosses between two bay scallops, Argopecten irradians concentricus Say and A-irradians irradians Lamarck

A complete diallel cross between two bay scallop populations, Argopecten irradians concentricus Say (M) and A. irradians irradians Lamarck (C), was carried out. Growth and survival were compared among hybrids and pure populations. No significant difference in the shell length was found among the four groups on the first day of D-larvae. On day 10, shell lengths of the two reciprocal crosses (CM, MC)(female x male ) were significantly greater than those of the CC (141.97 mu m) and MM (146.20 mu m) groups, with the growth rate of the MC (156.14 mu m) cross greater than that of the CM (155.35 mu m) cross. Also, heterosis for survival was significantly larger than that for growth. Both maternal origin and mating strategy had significant effects on growth and survival throughout the whole larval stage. Heterosis was also observed in later spat and adult stages. On day 170, the mean shell length, shell height and total weight of the CM cross were significantly larger than those of the other crosses (P<0.05). The results from this study indicate that hybridization between A. irradians concentricus and A. irradians irradians may be a promising way for genetic improvement of existing bay scallop brood stocks in China. (c) 2007 Elsevier B.V. All rights reserved.

The role of the TRAF-interacting protein in proliferation and differentiation.

Ubiquitination of proteins is a post-translational modification, which decides on the cellular fate of the protein. Addition of ubiquitin moieties to proteins is carried out by the sequential action of three enzymes: E1, ubiquitin-activating enzyme; E2, ubiquitin-conjugating enzyme; and E3, ubiquitin ligase. The TRAF-interacting protein (TRAIP, TRIP, RNF206) functions as Really Interesting New Gene (RING)-type E3 ubiquitin ligase, but its physiological substrates are not yet known. TRAIP was reported to interact with TRAF [tumor necrosis factor (TNF) receptor-associated factors] and the two tumor suppressors CYLD and Syk (spleen tyrosine kinase). Ectopically expressed TRAIP was shown to inhibit nuclear factor-kappa B (NF-κB) signalling. However, recent results suggested a role for TRAIP in biological processes other than NF-κB regulation. Knock-down of TRAIP in human epidermal keratinocytes repressed cellular proliferation and induced a block in the G1/S phase of the cell cycle without affecting NF-κB signalling. TRAIP is necessary for embryonal development as mutations affecting the Drosophila homologue of TRAIP are maternal effect-lethal mutants, and TRAIP knock-out mice die in utero because of aberrant regulation of cell proliferation and apoptosis. These findings underline the tight link between TRAIP and cell proliferation. In this review, we summarize the data on TRAIP and put them into a larger perspective regarding the role of TRAIP in the control of tissue homeostasis.

Functional Analysis of saxophone, the Drosophila Gene Encoding the BMP Type I Receptor Ortholog of Human ALK1/ACVRL1 and ACVR1/ALK2

In metazoans, bone morphogenetic proteins (BMPS) direct a myriad of developmental and adult homeostatic evens through their heterotetrameric type I and type II receptor complexes. We examined 3 existing and 12 newly generated mutations in the Drosophila type I receptor gene, saxophone (sax), the ortholog of the human Activin Receptor-Like. Kinasel and -2 (ALK1/ACVR1 and ALK2/ACVR1) genes. Our genetic analyses identified two distinct classes of sax alleles. The first class consists of homozygous viable gain-of-function (GOF) alleles that exhibit (1) synthetic lethality in combination with mutations in BMP pathway components, and (2) significant maternal effect lethality that can be rescued by an increased dosage of the BMP encoding gene, dpp(+). In contrast, the second class consists of alleles that are recessive lethal and do not exhibit lethality in combination with mutations in other BMP pathway components. The alleles in this second class are clearly loss-of-function (LOF) with both complete and partial loss-of-function mutations represented. We find that one allele in the second class of recessive lethals exhibits dominant-negative behavior, albeit distinct from the GOF activity of the first class of viable alleles. On the basis of the fact that the first class of viable alleles can be reverted to lethality and on our ability to independently generate recessive lethal sat mutations, our analysis demonstrates that sax is an essential gene. Consistent with this conclusion, we find that a normal sax transcript is produced by sax(P), a viable allele previously reported to be mill, and that this allele can be reverted to lethality. Interestingly, we determine that two mutations in the first: class of sax alleles show the same amino acid substitutions as mutations in the human receptors ALK1/ACVR1-1 and ACVR1/ALK2, responsible for cases of hereditary hemorrhagic telangiectasia type 2 (HHT2) and fibrodysplasia ossificans progressiva (FOP), respectively. Finally, the data presented here identify different functional requirements for the Sax receptor, support the proposal that Sax participates in a heteromeric receptor complex, and provide a mechanistic framework for future investigations into disease states that arise from defects in BMP/TGF-beta signaling.

Herdabilidade e correlações quanto a peso, perímetro escrotal e escores visuais à desmama, em bovinos Canchim

O objetivo deste trabalho foi estabelecer o modelo mais adequado para avaliação genética de bovinos Canchim e estimar os parâmetros genéticos de características produtivas à desmama. Foram utilizados dados de: 12.103 animais, quanto ao peso (PD); 5.278, quanto ao perímetro escrotal (PE); 8.343, quanto ao escore visual da conformação frigorífica (CF); 9.111, quanto ao escore de umbigo (UM); e 7.986, quanto ao escore de pelame (PEL). Os modelos estatísticos incluíram os efeitos fixos e os efeitos aleatórios genéticos aditivos direto, materno e de ambiente permanente materno, em diferentes combinações. As análises foram feitas pelo método da máxima verossimilhança restrita livre de derivadas. O modelo completo foi o mais adequado para PD, PE, CF e UM, enquanto o modelo com uso apenas dos efeitos genéticos aditivos direto e materno foi o mais adequado para PEL. As estimativas de herdabilidade direta foram 0,17, 0,13, 0,20, 0,18, e 0,52 para PD, PE, CF, UM e PEL, respectivamente, o que indica a possibilidade de se obter progresso genético por meio da seleção para essas características, principalmente para PEL. As correlações genéticas aditivas diretas entre as características variaram de -0,16 a 0,61. As correlações entre PD e PE e entre PD e CF indicam que a seleção para PD deve proporcionar ganho genético em PE e CF

Estimação de funções de covariância para características de crescimento da raça Tabapuã utilizando modelos de regressão aleatória

Foram utilizados 35.732 registros de peso do nascimento aos 660 dias de idade de 8.458 animais da raça Tabapuã para estimar funções de covariância utilizando modelos de regressão aleatória sobre polinômios de Legendre. Os modelos incluíram: como aleatórios, os efeitos genético aditivo direto, materno, de ambiente permanente de animal e materno; como fixos, os efeitos de grupo de contemporâneo; como covariáveis, a idade do animal à pesagem e a idade da vaca ao parto (linear e quadrática); e sobre a idade à pesagem, polinômio ortogonal de Legendre (regressão cúbica) foi considerado para modelar a curva média da população. O resíduo foi modelado considerando sete classes de variância e os modelos foram comparados pelos critérios de informação Bayesiano de Schwarz e Akaike. O melhor modelo apresentou ordens 4, 3, 6, 3 para os efeitos genético aditivo direto e materno, de ambiente permanente de animal e materno, respectivamente. As estimativas de covariância e herdabilidades, obtidas utilizando modelo bicaracter, e de regressão aleatória foram semelhantes. As estimativas de herdabilidade para o efeito genético aditivo direto, obtidas com o modelo de regressão aleatória, aumentaram do nascimento (0,15) aos 660 dias de idade (0,45). Maiores estimativas de herdabilidade materna foram obtidas para pesos medidos logo após o nascimento. As correlações genéticas variaram de moderadas a altas e diminuíram com o aumento da distância entre as pesagens. A seleção para maiores pesos em qualquer idade promove maior ganho de peso do nascimento aos 660 dias de idade.