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M. W. Hardisty - One of the best experts on this subject based on the ideXlab platform.
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sex differentiation and Gonadogenesis in lampreys part i and ii
Journal of Zoology, 2010Co-Authors: M. W. HardistyAbstract:The development of the gonad and the processes of sex differentiation have been studied in the ammocoete of Lampetra planeri, with particular emphasis on the mode of differentiation of the male gonads. After an initial undifferentiated stage during the first larval year, meiotic changes appear, particularly in cell nests, and from these germ cells and from isolated gonocytes, growing oocytes are developed. The initial phase of differentiation is regarded as a female stage, during which auxocytosis occurs on a variable scale in probably all gonads. This is followed in definitive males, by the degeneration of germ cells that have already differentiated in a female sense, either at the early meiotic prophase, or later in the cytoplasmic growth period of the occyte. Even in morphologically differentiated testes, meiotic activity and oocyte growth may be observed, although on a diminishing scale, throughout the greater part of the larval period. More extensive and synchronous atresia of growing oocytes may occur comparatively late in the larval period, giving the appearance of sex inversion. These cases are regarded as examples of abnormally retarded differentiation. Other presumptive male gonads are derived from gonads consisting predominantly of meiotic cysts, which have persisted beyond the age when auxocytosis is normally completed in definitive females. In some cases the future male gonad can be recognized at an early stage by certain morphological and histological criteria, irrespective of the condition of the germ cells. The views of Okkelberg (1921) and D'Ancona (1943, 1949) on the supposed existence of intersexual gonads have been discussed in relation to the quantitative analysis of gonad types. The author believes that the sexual indeterminacy attributed to these animals is illusory and that once differentiation has begun, its course and direction are irreversible. In male differentiation there is some evidence of renewed activity in the peritoneal epithelium of the gonad surface and it is suggested that the somatic elements of the testis may have some inductive effect tending to inhibit the further differentiation of bipotential germ cells in a female direction. No continuity exists between the undifferentiated cell nests of early stages and the cysts of germ cells in the mature testis. The former should not, therefore, be regarded as male elements in an hermaphrodite gonad. At early stages of differentiation, potential male ammocoetes are those in which the gonads are composed predominantly of meiotic cysts, or in which regression is taking place at various phases of oogenesis. The critical period for oocyte growth and for male differentiation occurs at lengths of 60 to 70 mm when the ammocoetes are at the beginning of their third year. From 50 mm upwards the proportion of female gonads consistently exceeds 50% of the total of all types. Analysis of ammocoete populations suggests that there is normally a slight excess of females, but that the sex ratios do not vary widely from one stream to another. No evidence has been found to suggest that environmental factors play any part in sex differentiation or that the sex orientation of the gonad is labile and indeterminate.
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Gonadogenesis and sex differentiation in the southern hemisphere lamprey Mordacia mordax
Journal of Zoology, 1992Co-Authors: M. W. Hardisty, Ian C. Potter, J. D. KoehnAbstract:Gonadal development and sex differentiation have been studied in larvae, metamorphosing individuals and young adults of the lamprey Mordacia mordax (Richardson), one of the two anadromous species of the southern hemisphere family Mordaciidae. The parasitic species is remarkable for the fact that its fecundity is so low that it is little greater than those of dwarf nonparasitic species. The relationship between the phasing of gonadal development, pattern of sex differentiation and fecundity in M. mordax is compared with those of nonparasitic and parasitic northern hemisphere lampreys (Petromyzontidae) and with that ofGeoiria australis, the sole representative of the other southern hemisphere family (Geotriidae). Up to lengths of 50 mm, the gonads have only small numbers of germ cells and are small and histologically undifferentiated. A marked increase in germ cell number occurs at body lengths of 50–70 mm, when in future ovaries, many secondary gonia enter meiotic prophase leading to cytoplasmic oocyte growth. Differentiation of the ovaries is generally completed at 90 mm, when they constitute just over half of all gonads. Throughout larval life and even during metamorphosis, the future male gonads remain small, histologically undifferentiated and indistinguishable from earlier undifferentiated stages. As in nonparasitic species, sex differentiation is characterized by the appearance in future male gonads of a high proportion of variable numbers of female orientated germ cells (in meiotic prophase or oocyte growth) destined to undergo atresia. In this respect, M. mordax is closer to the patterns seen in nonparasitic species, than to the more direct or determinate types of gonadal sex differentiation of the parasitic species with high fecundity, such as the southern hemisphere Geolria australis and similar holarctic species. It is suggested that variations in the nature and course of sex differentiation in lampreys may be dependent on initial sex differences in germ cell numbers and hence on the size and rate of growth of the gonad.
David Crews - One of the best experts on this subject based on the ideXlab platform.
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genetic network underlying temperature dependent sex determination is endogenously regulated by temperature in isolated cultured trachemys scripta gonads
Developmental Dynamics, 2010Co-Authors: Christina M Shoemakerdaly, Yuiko Matsumoto, Kyle R Jackson, Ryohei Yatsu, David CrewsAbstract:In reptiles with temperature-dependent sex determination, Gonadogenesis is initially directed by the incubation temperature of the egg during the middle third of embryonic development. The mechanism by which temperature is transduced into a sex-determining molecular signal remains a mystery, and here we examine the molecular network underlying sex determination in gonads in vitro. We use a whole organ culture system to show that expression of putative members of the sex-determining network (Dmrt1, Sox9, Mis, and FoxL2) are regulated by temperature endogenously within cells in the bipotential gonad and do not require other embryonic tissues to be expressed in a normal pattern in the red-eared slider turtle, Trachemys scripta. Furthermore, following a change in temperature, these factors exhibit temperature-responsive expression patterns that last for the duration of Gonadogenesis. Finally, mosaic misexpression of a fusion Sox9 construct demonstrates the ability to functionally manipulate the gonad at the molecular level. Developmental Dynamics 239:1061–1075, 2010. © 2010 Wiley-Liss, Inc.
Judith Kimble - One of the best experts on this subject based on the ideXlab platform.
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mig 38 a novel gene that regulates distal tip cell turning during Gonadogenesis in c elegans hermaphrodites
Developmental Biology, 2012Co-Authors: Maria Martynovsky, Judith Kimble, Ming Ching Wong, Dana T Byrd, Jean E SchwarzbauerAbstract:In Caenorhabditis elegans gonad morphogenesis, the final U-shapes of the two hermaphrodite gonad arms are determined by migration of the distal tip cells (DTCs). These somatic cells migrate in opposite directions on the ventral basement membrane until specific extracellular cues induce turning from ventral to dorsal and then centripetally toward the midbody region on the dorsal basement membrane. To dissect the mechanism of DTC turning, we examined the role of a novel gene, F40F11.2/mig-38, whose depletion by RNAi results in failure of DTC turning so that DTCs continue their migration away from the midbody region. mig-38 is expressed in the gonad primordium, and expression continues throughout DTC migration where it acts cell-autonomously to control DTC turning. RNAi depletion of both mig-38 and ina-1, which encodes an integrin adhesion receptor, enhanced the loss of turning phenotype indicating a genetic interaction between these genes. Furthermore, the integrin-associated protein MIG-15/Nck-interacting kinase (NIK) works with MIG-38 to direct DTC turning as shown by mig-38 RNAi with the mig-15(rh80) hypomorph. These results indicate that MIG-38 enhances the role of MIG-15 in integrin-dependent DTC turning. Knockdown of talin, a protein that is important for integrin activation, causes the DTCs to stop migration prematurely. When both talin and MIG-38 were depleted by RNAi treatment, the premature stop phenotype was suppressed. This suppression effect was reversed upon additional depletion of MIG-15 or its binding partner NCK-1. These results suggest that both talin and the MIG-15/NCK-1 complex promote DTC motility and that MIG-38 may act as a negative regulator of the complex. We propose a model to explain the dual role of MIG-38 in motility and turning.
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c elegans hlh 2 e daughterless controls key regulatory cells during Gonadogenesis
Developmental Biology, 2009Co-Authors: Michael A Chesney, Ngan Lam, Dyan E Morgan, Bryan T Phillips, Judith KimbleAbstract:The Caenorhabditis elegans distal tip cell (DTC) provides a niche for germline stem cells in both hermaphrodites and males. The hermaphrodite distal tip cell (hDTC) also provides "leader" function to control gonadal elongation and shape, while in males, leader function is allocated to the linker cell (LC). Therefore, the male distal tip cell (mDTC) serves as a niche but not as a leader. The C. elegans homolog of E/Daughterless, HLH-2, was previously implicated in hDTC specification. Here we report that HLH-2 is also critical for hDTC maintenance, hDTC niche function and hDTC expression of a lag-2/DSL ligand reporter. We also find that HLH-2 functions in males to direct linker cell specification and to promote both mDTC maintenance and the mDTC niche function. We conclude that HLH-2 functions in both sexes to promote leader cell specification and DTC niche function.
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the c elegans hand gene controls embryogenesis and early Gonadogenesis
Development, 2003Co-Authors: Laura D Mathies, Samuel T Henderson, Judith KimbleAbstract:The C. elegans genome encodes a single Hand bHLH transcription factor. Either hnd-1(RNAi) or a hnd-1 deletion causes partially penetrant defects in viability and Gonadogenesis. Dead embryos and young larvae are often misshapen at the posterior end. Our primary focus has been the role of hnd-1 in Gonadogenesis. Wild-type C. elegans has two somatic gonadal precursors and two primordial germ cells in stereotyped positions within its four-celled gonadal primordium. The hnd-1 gene affects the presence and position of both the somatic gonadal precursors and primordial germ cells within the primordium, but does not appear to have any role in later Gonadogenesis. hnd-1 probably acts within the somatic gonadal precursors or their mesodermal predecessors; defects in primordial germ cells and germ line appear to be secondary. In hnd-1 mutants, somatic gonadal precursors are generated normally, but are not maintained properly and sometimes die. A similar role in controlling the maintenance of precursor fates has been described for other genes governing early organogenesis, including the zebrafish Hand gene hands off. We also report the discovery of two genes, ehn-1 and ehn-3, that have overlapping functions with hnd-1 in embryogenesis and Gonadogenesis.
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pop 1 controls axis formation during early Gonadogenesis in c elegans
Development, 2002Co-Authors: Kellee R Siegfried, Judith KimbleAbstract:The shape and polarity of the C. elegans gonad is defined during early Gonadogenesis by two somatic gonadal precursor cells, Z1 and Z4, and their descendants. Z1 and Z4 divide asymmetrically to establish the proximal-distal axes of the gonad and to generate regulatory leader cells that control organ shape. In this paper, we report that pop-1, the C. elegans TCF/LEF-1 transcription factor, controls the first Z1/Z4 asymmetric division and hence controls proximal-distal axis formation. We have identified two pop-1(Sys) alleles (for symmetrical sisters) that render the Z1/Z4 divisions symmetrical. The pop-1(q645) allele is fully penetrant for the Sys Gonadogenesis defect in hermaphrodites, but affects male gonads weakly; pop-1(q645) alters a conserved amino acid in the β-catenin binding domain. The pop-1(q624) allele is weakly penetrant for multiple defects and appears to be a partial loss-of-function mutation; pop-1(q624) alters a conserved amino acid in the HMG-box DNA binding domain. Zygotic pop-1(RNAi) confirms the role of pop-1 in Z1/Z4 asymmetry and reveals additional roles of pop-1, including one in leader cell migration. Two other Wnt pathway regulators, wrm-1 and lit-1 , have the same effect as pop-1 on Z1/Z4 asymmetry. Therefore, wrm-1 and lit-1 are required for pop-1 function, rather than opposing it as observed in the early embryo. We conclude that POP-1 controls the Z1/Z4 asymmetric division and thereby establishes the proximal-distal axes of the gonad. This control over proximal-distal polarity extends our view of Wnt signaling in C. elegans , which had previously been known to control anterior-posterior polarities.
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the sys 1 gene and sexual dimorphism during Gonadogenesis in caenorhabditis elegans
Developmental Biology, 2001Co-Authors: Jennifer Miskowski, Judith KimbleAbstract:Abstract In wild-type Caenorhabditis elegans, the hermaphrodite gonad is a symmetrical structure, whereas the male gonad is asymmetric. Two cellular processes are critical for the generation of these sexually dimorphic gonadal shapes during early larval development. First, regulatory “leader” cells that control tube extension and gonadal shape are generated. Second, the somatic gonadal precursor cells migrate and become rearranged to establish the adult pattern. In this paper, we introduce sys-1, a gene required for early organization of the hermaphrodite, but not the male, gonad. The sys-1(q544) allele behaves genetically as a strong loss-of-function mutant and putative null. All hermaphrodites that are homozygous for sys-1(q544) possess a grossly malformed gonad and are sterile; in contrast, sys-1(q544) males exhibit much later and only partially penetrant gonadal defects. The sys-1(q544) hermaphrodites exhibit two striking early gonadal defects. First, the cell lineages of Z1 and Z4, the somatic gonadal progenitor cells, produce extra cells during L2, but the regulatory cells that control gonadal shape are not generated. Second, somatic gonadal precursor cells do not cluster centrally during late L2, and the somatic gonadal primordium typical of hermaphrodites is not established. In contrast, the early male gonadal lineage is asymmetric as normal, the somatic gonadal primordium typical of males is established correctly, and the male adult gonadal structures can be normal. We conclude that the primary role of sys-1 is to establish the shape and polarity of the hermaphrodite gonad.
Craig A. Smith - One of the best experts on this subject based on the ideXlab platform.
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applying single cell analysis to Gonadogenesis and dsds disorders differences of sex development
International Journal of Molecular Sciences, 2020Co-Authors: Martin A Estermann, Craig A. SmithAbstract:The gonads are unique among the body's organs in having a developmental choice: testis or ovary formation. Gonadal sex differentiation involves common progenitor cells that form either Sertoli and Leydig cells in the testis or granulosa and thecal cells in the ovary. Single-cell analysis is now shedding new light on how these cell lineages are specified and how they interact with the germline. Such studies are also providing new information on gonadal maturation, ageing and the somatic-germ cell niche. Furthermore, they have the potential to improve our understanding and diagnosis of Disorders/Differences of Sex Development (DSDs). DSDs occur when chromosomal, gonadal or anatomical sex are atypical. Despite major advances in recent years, most cases of DSD still cannot be explained at the molecular level. This presents a major pediatric concern. The emergence of single-cell genomics and transcriptomics now presents a novel avenue for DSD analysis, for both diagnosis and for understanding the molecular genetic etiology. Such -omics datasets have the potential to enhance our understanding of the cellular origins and pathogenesis of DSDs, as well as infertility and gonadal diseases such as cancer.
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the long non coding rna mhm plays a role in chicken embryonic development including Gonadogenesis
Developmental Biology, 2012Co-Authors: Kelly N Roeszler, Craig A. Smith, Andrew H Sinclair, Catherine ItmanAbstract:MHM is a chicken Z chromosome-linked locus that is methylated and transcriptionally silent in male cells, but is hypomethylated and transcribed into a long non-coding RNA in female cells. MHM has been implicated in both localised dosage compensation and sex determination in the chicken embryo, but direct evidence is lacking. We investigated the potential role of MHM in chicken embryonic development, using expression analysis and retroviral-mediated mis-expression. At embryonic stages, MHM is only expressed in females. Northern blotting showed that both sense and antisense strands of the MHM locus are transcribed, with the sense strand being more abundant. Whole mount in situ hybridization confirmed that the sense RNA is present in developing female embryos, notably in gonads, limbs, heart, branchial arch and brain. Within these cells, the MHM RNA is localized to the nucleus. The antisense transcript is lowly expressed and has a cytoplasmic localization in cells. Mis-expression of MHM sense and antisense sequences results in overgrowth of tissues in which transcripts are predominantly expressed. This includes altered asymmetric ovarian development in females. In males, MHM mis-expression impairs gonadal expression of the testis gene, DMRT1. Both MHM sense and antisense mis-expression cause brain abnormalities, while MHM sense causes an increase in male-biased embryo mortality. These results indicate that MHM has a role in chicken normal embryonic development, including gonadal sex differentiation.
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gene expression during Gonadogenesis in the chicken embryo
Gene, 1999Co-Authors: Craig A. Smith, Matthijs J Smith, Andrew H SinclairAbstract:Genes implicated in vertebrate sex determination and differentiation were studied in embryonic chicken gonads using reverse transcription and the polymerase chain reaction (RT-PCR). Expression profiles were obtained during gonadal sex differentiation for AMH, SOX9, SOX3, the Wilm's Tumour gene, WT1, and the orphan nuclear receptor genes, SF1 and DAX1. Some of these genes showed sexually dimorphic expression profiles during gonadal development, whereas others were expressed at similar levels in both sexes. The gene encoding Anti-Mullerian hormone (AMH) was expressed in both sexes prior to and during sexual differentiation of the gonads, with levels of expression consistently higher in males than in females. SOX9 expression was male-specific, and was up-regulated after the detection of AMH transcripts. SOX3 expression was observed prior to clear SOX9 expression and was up-regulated in both sexes at the onset of gonadal sex differentiation (but declined later in development). The WT1 gene was highly expressed in both sexes, whereas SF1 expression was clearly higher in developing ovaries compared to testes. DAX1 transcripts were observed in both sexes at all stages examined, but expression appeared somewhat higher in developing ovaries. These expression profiles are analysed in terms of current theories of vertebrate sex determination.
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Sertoli cell differentiation and Gonadogenesis in Alligator mississippiensis
Journal of Experimental Zoology, 1994Co-Authors: Craig A. Smith, Jean M.p. JossAbstract:Temperature-dependent sex determination (TSD) was first described for a crocodilian in Alligator mississippiensis, in which egg incubation at 33°C produces 100% male hatchlings and incubation at 30°C produces 100% females. Ultrastructural signs of testis differentiation in embryos incubated at 33°C are first detected during days 28–34 (developmental stages 21–22), when small numbers of enlarged “presumptive” Sertoli cells (pre-Sertoli cells) appear in the gonadal medulla of most embryos. These pre-Sertoli cells proliferate and differentiate into Sertoli cells during stage 23 at 33°C (days 35–41), marking seminiferous cord formation. At 30°C, some pre-Sertoli-like cells are also present in the medulla, but they are less numerous than at 33°C and they do not differentiate into Sertoli cells. Ovary differentiation at 30°C is characterized by proliferation of cortical germs cells from day 39 (stage 22), closely followed by proliferation of somatic (pre-follicular) cells in the cortex and regression of the medullary cords from day 43 (stage 23). We hypothesize that TSD in the alligator might be a function of a temperature-derived mismatch between Sertoli cell differentiation and germ cell/cortex proliferation. © 1994 Wiley-Liss, Inc.
Andrew H Sinclair - One of the best experts on this subject based on the ideXlab platform.
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the long non coding rna mhm plays a role in chicken embryonic development including Gonadogenesis
Developmental Biology, 2012Co-Authors: Kelly N Roeszler, Craig A. Smith, Andrew H Sinclair, Catherine ItmanAbstract:MHM is a chicken Z chromosome-linked locus that is methylated and transcriptionally silent in male cells, but is hypomethylated and transcribed into a long non-coding RNA in female cells. MHM has been implicated in both localised dosage compensation and sex determination in the chicken embryo, but direct evidence is lacking. We investigated the potential role of MHM in chicken embryonic development, using expression analysis and retroviral-mediated mis-expression. At embryonic stages, MHM is only expressed in females. Northern blotting showed that both sense and antisense strands of the MHM locus are transcribed, with the sense strand being more abundant. Whole mount in situ hybridization confirmed that the sense RNA is present in developing female embryos, notably in gonads, limbs, heart, branchial arch and brain. Within these cells, the MHM RNA is localized to the nucleus. The antisense transcript is lowly expressed and has a cytoplasmic localization in cells. Mis-expression of MHM sense and antisense sequences results in overgrowth of tissues in which transcripts are predominantly expressed. This includes altered asymmetric ovarian development in females. In males, MHM mis-expression impairs gonadal expression of the testis gene, DMRT1. Both MHM sense and antisense mis-expression cause brain abnormalities, while MHM sense causes an increase in male-biased embryo mortality. These results indicate that MHM has a role in chicken normal embryonic development, including gonadal sex differentiation.
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temperature dependent sex determination in the american alligator expression of sf1 wt1 and dax1 during Gonadogenesis
Gene, 2000Co-Authors: Patrick S Western, Jenny L Harry, Jennifer Marshall A Graves, Andrew H SinclairAbstract:Abstract Sex determination in mammals and birds is chromosomal, while in many reptiles sex determination is temperature dependent. Morphological development of the gonads in these systems is conserved, suggesting that many of the genes involved in gonad development are also conserved. The genes SF1 , WT1 and DAX1 play various roles in the mammalian testis-determining pathway. SF1 and WT1 are thought to interact to cause male-specific gene expression during testis development, while DAX1 is believed to inhibit this male-specific gene expression. We have cloned SF1 and DAX1 from the American alligator, a species with temperature-dependent sex determination (TSD). SF1 , DAX1 and WT1 are expressed in the urogenital system/gonad throughout the period of alligator Gonadogenesis which is temperature sensitive. SF1 appears to be expressed at a higher level in females than in males. This SF1 expression pattern is concordant with the observed pattern during chicken Gonadogenesis, but opposite to that observed during mouse Gonadogenesis. Although the observed sexual dimorphism of gonadal SF1 expression in alligators and chickens is opposite that observed in the mouse, it is probable that SF1 is involved in control of gonadal steroidogenesis in all these vertebrates. DAX1 and WT1 are both expressed during stages 22–25 of both males and females. However, there appear to be no sex differences in the expression patterns of these genes. We conclude that DAX1 , WT1 and SF1 may be involved in gonadal development of the alligator. These genes may form part of a gonadal-development pathway which has been conserved through vertebrate evolution.
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gene expression during Gonadogenesis in the chicken embryo
Gene, 1999Co-Authors: Craig A. Smith, Matthijs J Smith, Andrew H SinclairAbstract:Genes implicated in vertebrate sex determination and differentiation were studied in embryonic chicken gonads using reverse transcription and the polymerase chain reaction (RT-PCR). Expression profiles were obtained during gonadal sex differentiation for AMH, SOX9, SOX3, the Wilm's Tumour gene, WT1, and the orphan nuclear receptor genes, SF1 and DAX1. Some of these genes showed sexually dimorphic expression profiles during gonadal development, whereas others were expressed at similar levels in both sexes. The gene encoding Anti-Mullerian hormone (AMH) was expressed in both sexes prior to and during sexual differentiation of the gonads, with levels of expression consistently higher in males than in females. SOX9 expression was male-specific, and was up-regulated after the detection of AMH transcripts. SOX3 expression was observed prior to clear SOX9 expression and was up-regulated in both sexes at the onset of gonadal sex differentiation (but declined later in development). The WT1 gene was highly expressed in both sexes, whereas SF1 expression was clearly higher in developing ovaries compared to testes. DAX1 transcripts were observed in both sexes at all stages examined, but expression appeared somewhat higher in developing ovaries. These expression profiles are analysed in terms of current theories of vertebrate sex determination.