Functional Test of a Naturally Occurred Tumor Modifier Gene Provides Insights to Melanoma Development.

Occurrence of degenerative interactions is thought to serve as a mechanism underlying hybrid unfitness. However, the molecular mechanisms underpinning the genetic interaction and how they contribute to overall hybrid incompatibilities are limited to only a handful of examples. A vertebrate model organism, , is used to study hybrid dysfunction and it has been shown from this model that diseases, such as melanoma, can occur in certain interspecies hybrids.

Dimerization of melanocortin 4 receptor controls puberty onset and body size polymorphism.

fish exhibit a clear phenotypic polymorphism in puberty onset and reproductive strategies of males. In and , 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.

New approaches concerning the testis of Astyanax lacustris (Characidae): immunohistochemical studies.

Astyanax lacustris, locally known as lambari-do-rabo-amarelo, is a study model for Neotropical fish. Testis of A. lacustris shows deep morphophysiological changes throughout the annual reproductive cycle.

Development of Ovaries and Sex Change in Fish: Bringing Potential into Action.

Background: Encompassing about half of the 60,000 species of vertebrates, fish display the greatest diversity of sex determination mechanisms among metazoans. As such that phylum offers a unique playground to study the impressive variety of gonadal morphogenetic strategies, ranging from gonochorism, with either genetic or environmental sex determination, to unisexuality, with either simultaneous or consecutive hermaphroditism.

Summary: From the two main types of gonads, the ovaries embrace the important role to produce the larger and non-motile gametes, which is the basis for the development of a future organism.

Evolution of the Degenerated Y-Chromosome of the Swamp Guppy, .

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 () 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.

The replaceable master of sex determination: bottom-up hypothesis revisited.

Different group of vertebrates and invertebrates demonstrate an amazing diversity of gene regulations not only at the top but also at the bottom of the sex determination genetic network. As early as 1995, based on emerging findings in and , Wilkins suggested that the evolution of the sex determination pathway evolved from the bottom to the top of the hierarchy. Based on our current knowledge, this review revisits the 'bottom-up' hypothesis and applies its logic to vertebrates.

Crosstalk Between Retinoic Acid and Sex-Related Genes Controls Germ Cell Fate and Gametogenesis in Medaka.

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.

Melanocortin 4 receptor signaling and puberty onset regulation in Xiphophorus swordtails.

Fish of the genus Xiphophorus provide a prominent example of genetic control of male body size and reproductive tactics. In X.nigrensis and X.

The sterlet sturgeon genome sequence and the mechanisms of segmental rediploidization.

Sturgeons seem to be frozen in time. The archaic characteristics of this ancient fish lineage place it in a key phylogenetic position at the base of the ~30,000 modern teleost fish species. Moreover, sturgeons are notoriously polyploid, providing unique opportunities to investigate the evolution of polyploid genomes.

The transcriptome of the newt Cynops orientalis provides new insights into evolution and function of sexual gene networks in sarcopterygians.

Amphibians evolved in the Devonian period about 400 Mya and represent a transition step in tetrapod evolution. Among amphibians, high-throughput sequencing data are very limited for Caudata, due to their largest genome sizes among terrestrial vertebrates. In this paper we present the transcriptome from the fire bellied newt Cynops orientalis.

Spatial and temporal expression pattern of sex-related genes in ovo-testis of the self-fertilizing mangrove killifish (Kryptolebias marmoratus).

In vertebrates, sex determination and differentiation comprehend a fine balance between female and male factors, leading the bipotential anlage to develop towards ovary or testis, respectively. Nevertheless, the mangrove killifish, (Kryptolebias marmoratus) a simultaneous hermaphroditic species, could overcome those antagonistic pathways and evolved to develop and maintain reproductively active ovarian and testicular tissues in the same organ. Morphological and mRNA localization analyzes of developing and adult gonads demonstrate that genes related to testis (dmrt1 and amh) and ovary differentiation (foxl2 and sox9a) follow the same expression pattern observed in gonochoristic species, thus functioning as two independent organs.

Increase of cortisol levels after temperature stress activates dmrt1a causing female-to-male sex reversal and reduced germ cell number in medaka.

In vertebrates, there is accumulating evidence that environmental factors as triggers for sex determination and genetic sex determination are not two opposing alternatives but that a continuum of mechanisms bridge those extremes. One prominent example is the model fish species Oryzias latipes which has a stable XX/XY genetic sex determination system, but still responds to environmental cues, where high temperatures lead to female-to-male sex reversal. However, the mechanisms behind are still unknown.

Analysis of the Role of the Mc4r System in Development, Growth, and Puberty of Medaka.

In mammals the melanocortin 4 receptor (Mc4r) signaling system has been mainly associated with the regulation of appetite and energy homeostasis. In fish of the genus (platyfish and swordtails) puberty onset is genetically determined by a single locus, which encodes the . Wild populations of are polymorphic for early and late-maturing individuals.

A novel evolutionary conserved mechanism of RNA stability regulates synexpression of primordial germ cell-specific genes prior to the sex-determination stage in medaka.

Dmrt1 is a highly conserved transcription factor, which is critically involved in regulation of gonad development of vertebrates. In medaka, a duplicate of dmrt1-acting as master sex-determining gene-has a tightly timely and spatially controlled gonadal expression pattern. In addition to transcriptional regulation, a sequence motif in the 3' UTR (D3U-box) mediates transcript stability of dmrt1 mRNAs from medaka and other vertebrates.

Intersex, Hermaphroditism, and Gonadal Plasticity in Vertebrates: Evolution of the Müllerian Duct and Amh/Amhr2 Signaling.

In vertebrates, sex organs are generally specialized to perform a male or female reproductive role. Acquisition of the Müllerian duct, which gives rise to the oviduct, together with emergence of the Amh/Amhr2 system favored evolution of viviparity in jawed vertebrates. Species with high sex-specific reproductive adaptations have less potential to sex reverse, making intersex a nonfunctional condition.

A Comparative View on Sex Differentiation and Gametogenesis Genes in Lungfish and Coelacanths.

Gonadal sex differentiation and reproduction are the keys to the perpetuation of favorable gene combinations and positively selected traits. In vertebrates, several gonad development features that differentiate tetrapods and fishes are likely to be, at least in part, related to the water-to-land transition. The collection of information from basal sarcopterygians, coelacanths, and lungfishes, is crucial to improve our understanding of the molecular evolution of pathways involved in reproductive functions, since these organisms are generally regarded as "living fossils" and as the direct ancestors of tetrapods.

Retinoic acid and meiosis induction in adult versus embryonic gonads of medaka.

In vertebrates, one of the first recognizable sex differences in embryos is the onset of meiosis, known to be regulated by retinoic acid (RA) in mammals. We investigated in medaka a possible meiotic function of RA during the embryonic sex determination (SD) period and in mature gonads. We found RA mediated transcriptional activation in germ cells of both sexes much earlier than the SD stage, however, no such activity during the critical stages of SD.

Molecular cloning and expression analysis of dmrt1 and sox9 during gonad development and male reproductive cycle in the lambari fish, Astyanax altiparanae.

Background: The dmrt1 and sox9 genes have a well conserved function related to testis formation in vertebrates, and the group of fish presents a great diversity of species and reproductive mechanisms. The lambari fish (Astyanax altiparanae) is an important Neotropical species, where studies on molecular level of sex determination and gonad maturation are scarce.

Methods: Here, we employed molecular cloning techniques to analyze the cDNA sequences of the dmrt1 and sox9 genes, and describe the expression pattern of those genes during development and the male reproductive cycle by qRT-PCR, and related to histology of the gonad.

Divergent expression regulation of gonad development genes in medaka shows incomplete conservation of the downstream regulatory network of vertebrate sex determination.

Genetic control of male or female gonad development displays between different groups of organisms a remarkable diversity of "master sex-determining genes" at the top of the genetic hierarchies, whereas downstream components surprisingly appear to be evolutionarily more conserved. Without much further studies, conservation of sequence has been equalized to conservation of function. We have used the medaka fish to investigate the generality of this paradigm.