Forkhead l2 is expressed in the ovary and represses the promoter activity of the steroidogenic acute regulatory gene

Mutation analysis of the FOXL2 gene in Chinese patients with blepharophimosis–ptosis–epicanthus inversus syndrome

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is an autosomal dominant disorder characterized by blepharophimosis, ptosis and epicanthus inversus. Based on the presence and absence of premature ovarian failure, two clinical types have been distinguished. Both types of BPES have been mapped to chromosome 3q23 and are mostly due to mutations of a forkhead transcription factor FOXL2 gene which locates at this region. We screened for FOXL2 mutations in Chinese patients with BPES. A novel mutation (g.901-930dup30) which could result in an expansion of the polyalanine tract was found in two BPES type II families and one sporadic case. In addition, a new g.952delC mutation was identified in two patients from a BPES family of undetermined type. The previously reported g.892C>T (p.Q219X) was also found in 12 patients from a large BPES family of type I. No mutations were detected in three other BPES families and three sporadic cases. So we speculate that in a fraction of the BPES patients the genetic defect may represent a change in gene dosage or a rearrangement outside the transcription unit of FOXL2.

TAF4b, a TBP associated factor, is required for oocyte development and function

Development of a fertilizable oocyte is a complex process that relies on the precise temporal and spatial expression of specific genes in germ cells and in surrounding somatic cells. Since female mice null for Taf4b, a TBP associated factor, are sterile, we sought to determine when during follicular development this phenotype was first observed. At postnatal day 3, ovaries of Taf4b null females contained fewer (P < 0.01) oocytes than ovaries of wild type and heterozygous Taf4b mice. However, expression of only one somatic cell marker Foxl2 was reduced in ovaries at day 15. Despite the reduced number of follicles, many proceed to the antral stage, multiple genes associated with granulosa cell differentiation and oocyte maturation were expressed in a normal pattern, and immature Taf4b null females could be hormonally primed to ovulate and mate. However, the ovulated cumulus oocyte complexes from the Taf4b null mice had fewer (P < 0.01) cumulus cells, and the oocytes were functionally abnormal. GVBD and polar body extrusion were reduced significantly (P < 0.01). The few oocytes that were fertilized failed to progress beyond the two-cell stage of development. Thus, infertility in Taf4b null female mice is associated with defects in early follicle formation, oocyte maturation, and zygotic cleavage following ovulation and fertilization.

Transcriptional factor FOXL2 interacts with DP103 and induces apoptosis

Blepharophimosis-ptosis-epicanthus inversus syndrome type I is an autosomal disorder caused by mutations in FOXL2 gene and associated with premature ovarian failure in women by a dominant inheritance. FOXL2 is a recently identified protein that belongs to forkhead family transcription factor, of which signaling pathways are still unknown. Here, we show that FOXL2 induces apoptosis in both Chinese hamster ovary cells and rat granulosa cells, and it interacts with DP103, a DEAD box-containing protein. Overexpression of DP103 itself did not affect cell viability while its coexpression with FOXL2 led to the potentiation of cell death. Our results present previously undiscovered functions of these proteins, an apoptotic activity of FOXL2 in the ovary and a modulating activity of DP103 by interacting with FOXL2.

Transcriptional regulation of early oogenesis: in search of masters

Transcription factors in the germline play important roles in ovary formation and folliculogenesis, and control both oocyte development and somatic cell function. Factor in the germline (Figla) and newborn ovary homeobox gene (Nobox) represent a growing number of oocyte-specific transcription factors that regulate genes unique to oocytes. Studies on oocyte-specific transcription factors are important in understanding the genetic pathways essential for oogenesis, pluripotency, and embryonic development. Likely, these genes regulate reproductive life span and represent candidate genes for reproductive disorders, such as premature ovarian failure, and infertility. Therefore, oocyte-specific transcription factors, and oocyte-specific genes regulated by such factors, are attractive tissue-specific pharmacological targets to regulate human fertility.

A new heterozygous mutation of the FOXL2 gene is associated with a large ovarian cyst and ovarian dysfunction in an adolescent girl with blepharophimosis/ptosis/epicanthus inversus syndrome

Blepharophimosis/ptosis/epicanthus inversus syndrome (BPES), an autosomal dominant syndrome in which eyelid malformation is associated with (type I BPES) or without premature ovarian failure (type II BPES). Mutations of a putative winged helix/forkhead transcription factor FOXL2 account for both types of BPES. We report on a 16-year-old adolescent girl with blepharophimosis and ptosis. Subsequently she developed oligomenorrhea, secondary amenorrhea for 6 months, and an extremely large cyst of one ovary. The cyst contained 8 l of cyst fluid and histopathology displayed a large corpus luteum cyst. Following laparotomy, gonadotropin levels were elevated (LH 17.2 U/l, FSH 29.4 U/l) and estradiol levels decreased (67 pmol/l). Because of clinical aspects of BPES and abnormal ovarian function we suspected a mutation of her FOXL2 gene and found a new in-frame mutation (904_939dup36) on one allele, leading to a 12 alanine expansion within the polyalanine domain. We conclude that the FOXL2 mutation 904_939dup36 may account not only for blepharophimosis and ptosis but also for ovarian dysfunction and growth of the large corpus luteum cyst. In contrast to known FOXL2 mutations with polyalanine expansions and association with BPES type II, clinical aspects of our girl may indicate some degree of ovarian dysfunction that might finally lead to BPES type I with premature ovarian failure.

Association of the mSin3A-histone deacetylase 1/2 corepressor complex with the mouse steroidogenic acute regulatory protein gene

Several factors have been identified in the transcriptional repression of the steroidogenic acute regulatory protein (StAR) gene promoter; yet, no associating corepressor complexes have been characterized for the mouse promoter in MA-10 mouse Leydig tumor cells. We now report that Sp3, CAGA element binding proteins, and a corepressor complex consisting of mSin3A, histone deacetylase (HDAC)1, and HDAC2 associates with a transcriptional repressor region within the mouse StAR promoter. 5'-Promoter deletion analysis localized the negative regulatory region between -180 and -150 bp upstream of the transcription start site, and mutations in both the CAGA and Sp binding elements were required to relieve the repression of basal StAR promoter activity. Protein-DNA binding analysis revealed Sp3 and specific CAGA element-binding protein(s) associated with the repressor region. Coimmunoprecipitation analysis identified the presence of the mSin3A, HDAC1, and HDAC2 corepressor complex in MA-10 cells. Furthermore, chromatin immunoprecipitation assays revealed Sp3, mSin3A, and HDAC1/2 association with the proximal region of the StAR promoter in situ. In addition, HDAC inhibition resulted in a dose-dependent activation of a mouse StAR reporter construct, whereas mutations within the repressor region diminished this effect by 44%. In sum, these data support a novel regulatory mechanism for transcriptional repression of the mouse StAR promoter by DNA binding of Sp3 and CAGA element-binding proteins, and association of the Sin3 corepressor complex exhibiting HDAC activity.

The endless quest for sex determination genes

Disorders in human sex determination cause defects in gonadal function and can result in a spectrum of abnormalities in the internal and external genitalia, ranging from relatively mild sexual ambiguities to complete sex reversal. Several genes involved in sex determination have been validated in humans, and activities of their gene products are being elucidated, particularly in mouse models. However, how these genes interact in an overall process remains far from clear, and it is probable that many additional genes are involved. Management of patients with pathologies in sex determination and subsequent differentiation is currently under debate, but will require not only an understanding of the multiple definitions of an individual's sex but also an increased knowledge of the molecular mechanisms involved in sex determination.