TY - JOUR A1 - Adolfi, Mateus C. A1 - Herpin, Amaury A1 - Martinez-Bengochea, Anabel A1 - Kneitz, Susanne A1 - Regensburger, Martina A1 - Grunwald, David J. A1 - Schartl, Manfred T1 - Crosstalk Between Retinoic Acid and Sex-Related Genes Controls Germ Cell Fate and Gametogenesis in Medaka JF - Frontiers in Cell and Developmental Biology N2 - Sex determination (SD) is a highly diverse and complex mechanism. In vertebrates, one of the first morphological differences between the sexes is the timing of initiation of the first meiosis, where its initiation occurs first in female and later in male. Thus, SD is intimately related to the responsiveness of the germ cells to undergo meiosis in a sex-specific manner. In some vertebrates, it has been reported that the timing for meiosis entry would be under control of retinoic acid (RA), through activation of Stra8. In this study, we used a fish model species for sex determination and lacking the stra8 gene, the Japanese medaka (Oryzias latipes), to investigate the connection between RA and the sex determination pathway. Exogenous RA treatments act as a stress factor inhibiting germ cell differentiation probably by activation of dmrt1a and amh. Disruption of the RA degrading enzyme gene cyp26a1 induced precocious meiosis and oogenesis in embryos/hatchlings of female and even some males. Transcriptome analyzes of cyp26a1–/–adult gonads revealed upregulation of genes related to germ cell differentiation and meiosis, in both ovaries and testes. Our findings show that germ cells respond to RA in a stra8 independent model species. The responsiveness to RA is conferred by sex-related genes, restricting its action to the sex differentiation period in both sexes. KW - sex determination KW - retinoic acid KW - meiosis KW - gametogenesis KW - medaka Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-222669 SN - 2296-634X VL - 8 ER - TY - JOUR A1 - Nanda, Indrajit A1 - Schories, Susanne A1 - Simeonov, Ivan A1 - Adolfi, Mateus Contar A1 - Du, Kang A1 - Steinlein, Claus A1 - Alsheimer, Manfred A1 - Haaf, Thomas A1 - Schartl, Manfred T1 - Evolution of the degenerated Y-chromosome of the swamp guppy, Micropoecilia picta JF - Cells N2 - The conspicuous colour sexual dimorphism of guppies has made them paradigmatic study objects for sex-linked traits and sex chromosome evolution. Both the X- and Y-chromosomes of the common guppy (Poecilia reticulata) are genetically active and homomorphic, with a large homologous part and a small sex specific region. This feature is considered to emulate the initial stage of sex chromosome evolution. A similar situation has been documented in the related Endler’s and Oropuche guppies (P. wingei, P. obscura) indicating a common origin of the Y in this group. A recent molecular study in the swamp guppy (Micropoecilia. picta) reported a low SNP density on the Y, indicating Y-chromosome deterioration. We performed a series of cytological studies on M. picta to show that the Y-chromosome is quite small compared to the X and has accumulated a high content of heterochromatin. Furthermore, the Y-chromosome stands out in displaying CpG clusters around the centromeric region. These cytological findings evidently illustrate that the Y-chromosome in M. picta is indeed highly degenerated. Immunostaining for SYCP3 and MLH1 in pachytene meiocytes revealed that a substantial part of the Y remains associated with the X. A specific MLH1 hotspot site was persistently marked at the distal end of the associated XY structure. These results unveil a landmark of a recombining pseudoautosomal region on the otherwise strongly degenerated Y chromosome of M. picta. Hormone treatments of females revealed that, unexpectedly, no sexually antagonistic color gene is Y-linked in M. picta. All these differences to the Poecilia group of guppies indicate that the trajectories associated with the evolution of sex chromosomes are not in parallel. KW - sex chromosomes KW - heterochromatin KW - Y chromosome degeneration KW - meiosis KW - synaptonemal complex KW - recombination KW - 5-methylcytosine KW - testosterone KW - sexual antagonistic genes KW - sex linked pigmentation pattern Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-267242 SN - 2073-4409 VL - 11 IS - 7 ER - TY - JOUR A1 - Dedukh, Dmitrij A1 - Da Cruz, Irene A1 - Kneitz, Susanne A1 - Marta, Anatolie A1 - Ormanns, Jenny A1 - Tichopád, Tomáš A1 - Lu, Yuan A1 - Alsheimer, Manfred A1 - Janko, Karel A1 - Schartl, Manfred T1 - Achiasmatic meiosis in the unisexual Amazon molly, Poecilia formosa JF - Chromosome Research N2 - Unisexual reproduction, which generates clonal offspring, is an alternative strategy to sexual breeding and occurs even in vertebrates. A wide range of non-sexual reproductive modes have been described, and one of the least understood questions is how such pathways emerged and how they mechanistically proceed. The Amazon molly, Poecilia formosa, needs sperm from males of related species to trigger the parthenogenetic development of diploid eggs. However, the mechanism, of how the unreduced female gametes are produced, remains unclear. Cytological analyses revealed that the chromosomes of primary oocytes initiate pachytene but do not proceed to bivalent formation and meiotic crossovers. Comparing ovary transcriptomes of P. formosa and its sexual parental species revealed expression levels of meiosis-specific genes deviating from P. mexicana but not from P. latipinna. Furthermore, several meiosis genes show biased expression towards one of the two alleles from the parental genomes. We infer from our data that in the Amazon molly diploid oocytes are generated by apomixis due to a failure in the synapsis of homologous chromosomes. The fact that this failure is not reflected in the differential expression of known meiosis genes suggests the underlying molecular mechanism may be dysregulation on the protein level or misexpression of a so far unknown meiosis gene, and/or hybrid dysgenesis because of compromised interaction of proteins from diverged genomes. KW - meiosis KW - parthenogenesis KW - synaptonemal complex KW - recombination KW - crossing-over KW - achiasmatic KW - transcriptome KW - oogenesis Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-325128 VL - 30 IS - 4 ER - TY - JOUR A1 - Sendell-Price, Ashley T. A1 - Tulenko, Frank J. A1 - Pettersson, Mats A1 - Kang, Du A1 - Montandon, Margo A1 - Winkler, Sylke A1 - Kulb, Kathleen A1 - Naylor, Gavin P. A1 - Phillippy, Adam A1 - Fedrigo, Olivier A1 - Mountcastle, Jacquelyn A1 - Balacco, Jennifer R. A1 - Dutra, Amalia A1 - Dale, Rebecca E. A1 - Haase, Bettina A1 - Jarvis, Erich D. A1 - Myers, Gene A1 - Burgess, Shawn M. A1 - Currie, Peter D. A1 - Andersson, Leif A1 - Schartl, Manfred T1 - Low mutation rate in epaulette sharks is consistent with a slow rate of evolution in sharks JF - Nature Communications N2 - Sharks occupy diverse ecological niches and play critical roles in marine ecosystems, often acting as apex predators. They are considered a slow-evolving lineage and have been suggested to exhibit exceptionally low cancer rates. These two features could be explained by a low nuclear mutation rate. Here, we provide a direct estimate of the nuclear mutation rate in the epaulette shark (Hemiscyllium ocellatum). We generate a high-quality reference genome, and resequence the whole genomes of parents and nine offspring to detect de novo mutations. Using stringent criteria, we estimate a mutation rate of 7×10\(^{−10}\) per base pair, per generation. This represents one of the lowest directly estimated mutation rates for any vertebrate clade, indicating that this basal vertebrate group is indeed a slowly evolving lineage whose ability to restore genetic diversity following a sustained population bottleneck may be hampered by a low mutation rate. KW - evolutionary genetics KW - genomics KW - molecular evolution Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-357827 VL - 14 ER - TY - JOUR A1 - Liu, Ruiqi A1 - Friedrich, Mike A1 - Hemmen, Katherina A1 - Jansen, Kerstin A1 - Adolfi, Mateus C. A1 - Schartl, Manfred A1 - Heinze, Katrin G. T1 - Dimerization of melanocortin 4 receptor controls puberty onset and body size polymorphism JF - Frontiers in Endocrinology N2 - Xiphophorus fish exhibit a clear phenotypic polymorphism in puberty onset and reproductive strategies of males. In X. nigrensis and X. multilineatus, puberty onset is genetically determined and linked to a melanocortin 4 receptor (Mc4r) polymorphism of wild-type and mutant alleles on the sex chromosomes. We hypothesized that Mc4r mutant alleles act on wild-type alleles by a dominant negative effect through receptor dimerization, leading to differential intracellular signaling and effector gene activation. Depending on signaling strength, the onset of puberty either occurs early or is delayed. Here, we show by Förster Resonance Energy Transfer (FRET) that wild-type Xiphophorus Mc4r monomers can form homodimers, but also heterodimers with mutant receptors resulting in compromised signaling which explains the reduced Mc4r signaling in large males. Thus, hetero- vs. homo- dimerization seems to be the key molecular mechanism for the polymorphism in puberty onset and body size in male fish. KW - fluorescence lifetime imaging microscopy KW - Förster Resonance Energy Transfer KW - Mc4r KW - puberty KW - Xiphophorus Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-354261 SN - 1664-2392 VL - 14 ER -