Intragenic Duplication of DMRT1 in a SRY-Negative Boy with 46,XX Disorder of Sex Development

Background. 46,XX disorders of sex development are rare. Approximately, 90% of XX males are SRY-positive, while testicular development in the absence of SRY takes place in a minority. Methods: A boy with 46,XX karyotype (SRY-negative; absence of SOX9 duplications) was investigated by targeted Next Generation Sequencing (NGS), Multiplex ligation-dependent probe amplification (MLPA), and Comparative Genomic Hybridization array (CGH-array). Results: The boy had normal male phenotype and normal prepubertal values of testicular hormones. He presented a heterozygous duplication of 49.626 bp, encompassing exons 2 and 3 of DMRT1. The result was arr[GRCh37] 9p24.3(845893_895518)x3. Since both breakpoints are harbored in the intronic regions, the duplication does not stop or shift the coding frame. Additional known pathogenic or uncertain variants in pro-testis gene cascade were not identified. Conclusions: This study report a boy with 46,XX testicular disorder of sex differentiation, showing a de novo partial intragenic duplication of DMRT1. This intragenic duplication may result in a gain of function, acting as primary pro-testis gene (or anti-ovary gene) in a 46,XX human foetus and permitting normal pre-pubertal endocrine testis function.

Conditional knockdown of transformer in sheep blow fly suggests a role in repression of dosage compensation and potential for population suppression

The transformer (tra) gene is essential for female development in many insect species, including the Australian sheep blow fly, Lucilia cuprina. Sex-specific tra RNA splicing is controlled by Sex lethal (Sxl) in Drosophila melanogaster but is auto-regulated in L. cuprina. Sxl also represses X chromosome dosage compensation in female D. melanogaster. We have developed conditional Lctra RNAi knockdown strains using the tet-off system. Four strains did not produce females on diet without tetracycline and could potentially be used for genetic control of L. cuprina. In one strain, which showed both maternal and zygotic tTA expression, most XX transformed males died at the pupal stage. RNAseq and qRT-PCR analyses of mid-stage pupae showed increased expression of X-linked genes in XX individuals. These results suggest that Lctra promotes somatic sexual differentiation and inhibits X chromosome dosage compensation in female L. cuprina. However, XX flies homozygous for a loss-of-function Lctra knockin mutation were fully transformed and showed high pupal eclosion. Two of five X-linked genes examined showed a significant increase in mRNA levels in XX males. The stronger phenotype in the RNAi knockdown strain could indicate that maternal Lctra expression may be essential for initiation of dosage compensation suppression in female embryos.

SEX DIFFERENCES IN BLOOD PRESSURE RESPONSE TO CONTINUOUS ANG II INFUSION: ARE ONLY SEX HORMONES TO BLAME?

To investigate the involvement of the sex chromosome complement (SCC), organizational and activational hormonal effects in changes in mean arterial pressure during acute Ang II infusion, we used gonadectomized (GDX) mice of the "four core genotypes" model, which dissociates the effect of gonadal sex and SCC, allowing comparisons of sexually dimorphic traits between XX and XY females as well as XX and XY males. Additionally, β-estradiol and testosterone propionate (2ug/g) were daily injected for 4 days to evaluate activational hormonal effects. Statistical analysis of the changes in mean arterial pressure revealed an interaction of SCC, organizational and activational hormonal effects during Ang II infusion {F(7,39=2,60 p<0.01)}. Our results indicate that, in absence of activational hormonal effects, interaction between the SCC and organizational hormonal action differentially modulates changes in arterial pressure. In GDX mice without hormone replacement, Ang II infusion resulted in an increase in mean arterial pressure in XX-male, XX-female and XY-female mice, while no changes were observed in XY-male mice. Furthermore, β-estradiol replacement (GDX+E2 group) resulted in a decrease in blood pressure in XX-males, XX-females and XY-females (indicating an activational β-estradiol effect), while no changes were observed in the XY-male group. Moreover, testosterone propionate replacement (GDX+TP group) showed a greater increase in blood pressure in XY-male mice than in XX-males and XX-females, demonstrating an activational hormonal effect of testosterone in XY-male mice. Our data isolates and highlights the contribution and interaction of SCC, activational and organizational hormonal effects in sex differences in Ang II blood pressure regulation.

Parental RNAi Silencing of the transformer-2 Gene in a Species of the Anastrepha fraterculus Complex of Cryptic Species (Diptera, Tephritidae)

In genera Anastrepha, Bactrocera and Ceratitis of the tephritid fruit flies the auto-regulatory function of gene transformer is assumed to be activated by maternal derived mRNA or the proteins of the gene transformer (tra-2 mat) and transformer-2 (tra-2mat). However, this maternal effect was not yet been demonstrated. The objective of the present study was to test the effect of absence of tra-2mat in the eggs on the sex determination of A. sp.1 affinis fraterculus. This was achieved by silencing gene tra-2 in the parental females via the pRNA interference. The data showed that tra-2 was transiently silenced in the female for three weeks period. The progenies sex ratio produced by these females during the silencing of tra-2 depart from 1:1 in favor of males. The excess of males was due to the transformation of a fraction of genotypical female XX embryos into XX males, the so-called pseudomales, Individual F1 males from the offspring of treated females crossed to females from the stock, revealed that majority of them showed regular mating behavior and were fertile. However, no offspring was produced in the crosses by a fraction of males that have produced sperms, showed regular mating behavior but did not transfer sperms to the females. The data allow the conclusion that the absence of tra-2mat in the eggs had impaired the self-regulation of the embryonic gene tra resulting in the transformation of XX embryos into pseudomales and also that these pseudomales are sterile. This effect may be useful improve more sustainable technologies for fruit fly control such as SIT.

Targeting the autosomal Ceratitis capitata transformer gene using Cas9 or dCas9 to masculinize XX individuals without inducing mutations

Background Females of the Mediterranean fruit fly Ceratitis capitata (Medfly) are major agricultural pests, as they lay eggs into the fruit crops of hundreds of plant species. In Medfly, female sex determination is based on the activation of Cctransformer (Cctra). A maternal contribution of Cctra is required to activate Cctra itself in the XX embryos and to start and epigenetically maintain a Cctra positive feedback loop, by female-specific alternative splicing, leading to female development. In XY embryos, the male determining Maleness-on-the-Y gene (MoY) blocks this activation and Cctra produces male-specific transcripts encoding truncated CcTRA isoforms and male differentiation occurs. Results With the aim of inducing frameshift mutations in the first coding exon to disrupt both female-specific and shorter male-specific CcTRA open reading frames (ORF), we injected Cas9 ribonucleoproteins (Cas9 and single guide RNA, sgRNA) in embryos. As this approach leads to mostly monoallelic mutations, masculinization was expected only in G1 XX individuals carrying biallelic mutations, following crosses of G0 injected individuals. Surprisingly, these injections into XX-only embryos led to G0 adults that included not only XX females but also 50% of reverted fertile XX males. The G0 XX males expressed male-specific Cctra transcripts, suggesting full masculinization. Interestingly, out of six G0 XX males, four displayed the Cctra wild type sequence. This finding suggests that masculinization by Cas9-sgRNA injections was independent from its mutagenic activity. In line with this observation, embryonic targeting of Cctra in XX embryos by a dead Cas9 (enzymatically inactive, dCas9) also favoured a male-specific splicing of Cctra, in both embryos and adults. Conclusions Our data suggest that the establishment of Cctra female-specific autoregulation during the early embryogenesis has been repressed in XX embryos by the transient binding of the Cas9-sgRNA on the first exon of the Cctra gene. This hypothesis is supported by the observation that the shift of Cctra splicing from female to male mode is induced also by dCas9. Collectively, the present findings corroborate the idea that a transient embryonic inactivation of Cctra is sufficient for male sex determination.

Gene-Level, but Not Chromosome-Wide, Divergence between a Very Young House Fly Proto-Y Chromosome and Its Homologous Proto-X Chromosome

X and Y chromosomes are usually derived from a pair of homologous autosomes, which then diverge from each other over time. Although Y-specific features have been characterized in sex chromosomes of various ages, the earliest stages of Y chromosome evolution remain elusive. In particular, we do not know whether early stages of Y chromosome evolution consist of changes to individual genes or happen via chromosome-scale divergence from the X. To address this question, we quantified divergence between young proto-X and proto-Y chromosomes in the house fly, Musca domestica. We compared proto-sex chromosome sequence and gene expression between genotypic (XY) and sex-reversed (XX) males. We find evidence for sequence divergence between genes on the proto-X and proto-Y, including five genes with mitochondrial functions. There is also an excess of genes with divergent expression between the proto-X and proto-Y, but the number of genes is small. This suggests that individual proto-Y genes, but not the entire proto-Y chromosome, have diverged from the proto-X. We identified one gene, encoding an axonemal dynein assembly factor (which functions in sperm motility), that has higher expression in XY males than XX males because of a disproportionate contribution of the proto-Y allele to gene expression. The upregulation of the proto-Y allele may be favored in males because of this gene’s function in spermatogenesis. The evolutionary divergence between proto-X and proto-Y copies of this gene, as well as the mitochondrial genes, is consistent with selection in males affecting the evolution of individual genes during early Y chromosome evolution.

Gene-level, but not chromosome-wide, divergence between a very young house fly proto-Y chromosome and its homologous proto-X chromosome

X and Y chromosomes are usually derived from a pair of homologous autosomes, which then diverge from each other over time. Although Y-specific features have been characterized in sex chromosomes of various ages, the earliest stages of Y chromosome evolution remain elusive. In particular, we do not know whether early stages of Y chromosome evolution consist of changes to individual genes or happen via chromosome-scale divergence from the X. To address this question, we quantified divergence between young proto-X and proto-Y chromosomes in the house fly, Musca domestica. We compared proto-sex chromosome sequence and gene expression between genotypic (XY) and sex-reversed (XX) males. We find evidence for sequence divergence between genes on the proto-X and proto-Y, including five genes with mitochondrial functions. There is also an excess of genes with divergent expression between the proto-X and proto-Y, but the number of genes is small. This suggests that individual proto-Y genes, but not the entire proto-Y chromosome, have diverged from the proto-X. We identified one gene, encoding an axonemal dynein assembly factor (which functions in sperm motility), that has higher expression in XY males than XX males because of a disproportionate contribution of the proto-Y allele to gene expression. The up-regulation of the proto-Y allele may be favored in males because of this gene’s function in spermatogenesis. The evolutionary divergence between proto-X and proto-Y copies of this gene, as well as the mitochondrial genes, is consistent with selection in males affecting the evolution of individual genes during early Y chromosome evolution.