Application of SNP in Genetic Sex Identification and Effect of Estradiol on Gene Expression of Sex-Related Genes in Strongylocentrotus intermedius

Sea urchin (Strongylocentrotus intermedius) is an economically important mariculture species in Asia, and its gonads are the only edible part. The efficiency of genetic breeding in sea urchins is hampered due to the inability to distinguish gender by appearance. In this study, we first identified a sex-associated single nucleotide polymorphism (SNP) by combining type IIB endonuclease restriction site-associated DNA sequencing (2b-RAD-seq) and genome survey. Importantly, this SNP is located within spata4, a gene specifically expressed in male. Knocking down of spata4 by RNA interference (RNAi) in male individuals led to the downregulation of other conserved testis differentiation-related genes and germ cell marker genes. We also revealed that sex ratio in this validated culture population of S. intermedius is not 1:1. Moreover, after a 58-day feeding experiment with estradiol, the expression levels of several conserved genes that are related to testis differentiation, ovary differentiation, and estrogen metabolism were dynamically changed. Taken together, our results will contribute toward improving breeding efficiency, developing sex-controlled breeding, and providing a solid base for understanding sex determination mechanisms in sea urchins.

Loss of Mafb and Maf distorts myeloid cell ratios and disrupts fetal mouse testis vascularization and organogenesis†

Testis differentiation is initiated when Sry in pre-Sertoli cells directs the gonad toward a male-specific fate. Sertoli cells are essential for testis development, but cell types within the interstitial compartment, such as immune and endothelial cells, are also critical for organ formation. Our previous work implicated macrophages in fetal testis morphogenesis, but little is known about genes underlying immune cell development during organogenesis. Here we examine the role of the immune-associated genes Mafb and Maf in mouse fetal gonad development, and we demonstrate that deletion of these genes leads to aberrant hematopoiesis manifested by supernumerary gonadal monocytes. Mafb; Maf double knockout embryos underwent initial gonadal sex determination normally, but exhibited testicular hypervascularization, testis cord formation defects, Leydig cell deficit, and a reduced number of germ cells. In general, Mafb and Maf alone were dispensable for gonad development; however, when both genes were deleted, we observed significant defects in testicular morphogenesis, indicating that Mafb and Maf work redundantly during testis differentiation. These results demonstrate previously unappreciated roles for Mafb and Maf in immune and vascular development and highlight the importance of interstitial cells in gonadal differentiation.

Loss of Mafb and Maf distorts myeloid cell ratios and disrupts fetal mouse testis vascularization and organogenesis

Testis differentiation is initiated when Sry in pre-Sertoli cells directs the gonad toward a male-specific fate. Sertoli cells are essential for testis development, but cell types within the interstitial compartment, such as immune and endothelial cells, are also critical for organ formation. Our previous work implicated macrophages in fetal testis morphogenesis, but little is known about genes underlying immune cell development during organogenesis. Here we examine the role of the immune-associated genes Mafb and Maf in mouse fetal gonad development, and we demonstrate that deletion of these genes leads to aberrant hematopoiesis manifested by supernumerary gonadal monocytes. Mafb;Maf double knockout embryos underwent initial gonadal sex determination normally, but exhibited testicular hypervascularization, testis cord formation defects, Leydig cell deficit, and a reduced number of germ cells. In general, Mafb and Maf alone were dispensable for gonad development; however, when both genes were deleted, we observed significant defects in testicular morphogenesis, indicating that Mafb and Maf work redundantly during testis differentiation. These results demonstrate previously unappreciated roles for Mafb and Maf in immune and vascular development and highlight the importance of interstitial cells in gonadal differentiation.Summary statementDeletion of Mafb and Maf genes leads to supernumerary monocytes in fetal mouse gonads, resulting in vascular, morphogenetic, and differentiation defects during testicular organogenesis.

Testis Development and Differentiation in Amphibians

Sex is determined genetically in amphibians; however, little is known about the sex chromosomes, testis-determining genes, and the genes involved in testis differentiation in this class. Certain inherent characteristics of the species of this group, like the homomorphic sex chromosomes, the high diversity of the sex-determining mechanisms, or the existence of polyploids, may hinder the design of experiments when studying how the gonads can differentiate. Even so, other features, like their external development or the possibility of inducing sex reversal by external treatments, can be helpful. This review summarizes the current knowledge on amphibian sex determination, gonadal development, and testis differentiation. The analysis of this information, compared with the information available for other vertebrate groups, allows us to identify the evolutionarily conserved and divergent pathways involved in testis differentiation. Overall, the data confirm the previous observations in other vertebrates—the morphology of the adult testis is similar across different groups; however, the male-determining signal and the genetic networks involved in testis differentiation are not evolutionarily conserved.