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Comment |
Koyano S, et al reported that the Xenopus Sox3 gene expressed in oocytes of early stages.
They isolated an SRY-type HMG box (Sox) cDNA, XSox3, from a Xenopus
immature ovary cDNA library. The XSox3 cDNA contains an open reading frame
(ORF) of 309 amino-acid residues, showing 62.7 and 77.0% homology with human
and chicken Sox3 proteins, respectively. XSox3 gene is
composed of a single exon by sequence analysis of the genomic clone and the
determination of the transcription start site of the XSox3. The XSox3 mRNA was
detected only in ovary and was at a higher level in immature ovary than in mature ovary.
During oocyte maturation, the XSox3 mRNA was most abundant in stage I oocytes,
and the XSox3 protein was detected in stage I and II oocytes. Recombinant XSox3
protein produced in Escherichia coli bound specifically to sequences containing the
binding motif for the HMG box of SRY or SOX proteins, AACAAT or AACAAAG,
demonstrating its sequence-specific DNA binding property. Taken together, these
results indicate that the XSox3 protein may participate in early oogenesis of Xenopus
as a transcription factor.Chiang EFL, et al 2001 reported two sox9 genes on duplicated zebrafish chromosomes and the expression
of similar transcription activators in distinct sites.
Sox9 is a transcription factor required for cartilage formation and testis
determination in mammals. The authors have cloned from zebrafish two sox9 genes, termed
sox9a and sox9b. Gene phylogenies showed that both genes are orthologous to
tetrapod SOX3 genes. Genetic mapping showed that these two loci reside on
chromosome segments that were apparently duplicated in a large-scale genomic
duplication event in ray fin fish phylogeny. Both Sox9a and Sox9b proteins
bind to the HMG consensus DNA sequences in vitro. In the adults, sox9a is expressed in
many tissues including brain, muscle, fin, and testis, whereas sox9b
expression is restricted to previtellogenic oocytes of the ovary.
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Mutations |
2 mutations
Species: mouse
Mutation name: None
type: null mutation
fertility: subfertile
Comment: Weiss J, et al reported that Sox3 is required for gonadal function, but not sex determination, in males and females.
Sox3 is expressed in developing gonads and in the brain. Evolutionary evidence suggests that the X-chromosomal Sox3 gene may be the ancestral precursor of Sry, a sex-determining gene, and Sox3 has been proposed to play a role in sex determination. However, patients with mutations in SOX3 exhibit normal gonadal determination but are mentally retarded and have short stature secondary to growth hormone (GH) deficiency. The authors used Cre-LoxP targeted mutagenesis to delete Sox3 from mice. Null mice of both sexes had no overt behavioral deficits and exhibited normal GH gene expression. Low body weight was observed for some mice; overgrowth and misalignment of the front teeth was observed consistently. Female Sox3 null mice (-/-) developed ovaries but had excess follicular atresia, ovulation of defective oocytes, and severely reduced fertility. Pituitary (luteinizing hormone and follicle-stimulating hormone) and uterine functions were normal in females. Hemizygous male null mice (-/Y) developed testes but were hypogonadal. Testis weight was reduced by 42%, and there was extensive Sertoli cell vacuolization, loss of germ cells, reduced sperm counts, and disruption of the seminiferous tubules. The authors conclude that Sox3 is not required for gonadal determination but is important for normal oocyte development and male testis differentiation and gametogenesis.
Species: None
Mutation name:
type: null mutation
fertility: subfertile
Comment: Loss-of-function of sox3 causes follicle development retardation and reduces fecundity in zebrafish. Hong Q et al. (2020) Folliculogenesis is essential for production of female gametes in vertebrates. However, the molecular mechanisms underlying follicle development, particularly apoptosis regulation in ovary, remain elusive. Here, we generated sox3 knockout zebrafish lines using CRISPR/Cas9. sox3 knockout led to follicle development retardation and a reduced fecundity in females. Comparative analysis of transcriptome between sox3-/- and wild-type ovaries revealed that Sox3 was involved in pathways of ovarian steroidogenesis and apoptosis. Knockout of sox3 promoted follicle apoptosis and obvious apoptosis signals were detected in somatic cells of stages III and IV follicles of sox3-/- ovaries. Moreover, Sox3 can bind to and activate the promoter of cyp19a1a. Up-regulation of Cyp19a1a expression promoted 17β-estradiol synthesis, which inhibited apoptosis in follicle development. Thus, Sox3 functions as a regulator of Cyp19a1a expression, via 17β-E2 linking apoptosis suppression, which is implicated in improving female fecundity.//////////////////
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