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Results for “Forkhead Box Protein L2”

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At least 19 recordsLinked to original sources

PubMed2004

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

Premature ovarian failure in a subgroup of women with blepharophimosis-ptosis-epicanthus inversus type 1 syndrome has been associated with nonsense mutations in the gene encoding a Forkhead transcription factor, Forkhead L2 (FOXL2). However, the exact function of FOXL2 in the ovary is unclear. We investigated the expression of FOXL2 in the mouse ovary during follicular development and maturation by RT-PCR and in situ hybridization. The FOXL2 mRNA is expressed in ovaries throughout development and adulthood and is localized to the undifferentiated granulosa cells in small and medium follicles as well as cumulus cells of preovulatory follicles. FOXL2 belongs to a group of transcription factors capable of interacting with specific DNA sequences in diverse gene promoters. With the presence of multiple putative forkhead DNA consensus sites, the promoter of the human steroidogenic acute regulatory (StAR) gene was used to test for regulation by FOXL2. Cotransfection studies revealed that wild-type FOXL2 represses the activity of the StAR promoter, and the first 95 bp upstream of the transcriptional start site of the StAR gene is sufficient for FOXL2 repression. EMSAs confirmed that FOXL2 interacts directly with this region. Analyses using FOXL2 mutants also demonstrated the importance of the entire alanine/proline-rich carboxyl terminus of FOXL2 for transcriptional repression. Furthermore, these mutations produce a protein with a dominant-negative effect that disables the transcriptional repressor activity of wild-type FOXL2. Dominant-negative mutations of FOXL2 could increase expression of StAR and other follicle differentiation genes in small and medium follicles to accelerate follicle development, resulting in increased initial recruitment of dormant follicles and thus the premature ovarian failure phenotype.

Alanine↗

PubMed2002

Genes and translocations involved in POF.

Changes at a single autosomal locus and many X-linked loci have been implicated in women with gonadal dysgenesis [premature ovarian failure (POF) with deficits in ovarian follicles]. For the chromosome 3 locus, a forkhead transcription factor gene (FOXL2) has been identified, in which lesions result in decreased follicles by haploinsufficiency. In contrast, sporadic X; autosomal translocations are distributed at many points on the X, but concentrate in a critical region on Xq. The association of the breakpoints with genes involved in ovarian function is thus far weak (in four analyzed cases) and has not been related to pathology in other POF patients. While many more translocations can be analyzed in detail as the human genome sequence is refined, it remains possible that translocations like X monosomy (Turner syndrome) lead to POF not by interrupting specific genes important in ovarian development, but by causing aberrations in pairing or X-inactivation during folliculogenesis. It is noted that the critical region has unusual features, neighboring the X-inactivation center and including an 18 Mb region of very low recombination. These suggest that chromosome dynamics in the region may be sensitive to structural changes, and when modified by translocations might provoke apoptosis at meiotic checkpoints. Choices among models for the etiology of POF should be feasible based on studies of ovarian follicle development and attrition in mouse models. Studies would prominently include gene expression profiling of developmental-specific pathways in nascent ovaries with controlled levels of Foxl2 and interacting proteins, or with defined changes in the X chromosome.

Chromosomes, Human, X↗

PubMed2002

Mutations in FOXL2 underlying BPES (types 1 and 2) in Colombian families.

We report the genetic characterization of one family with blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) type 1 and two families with BPES type 2 from a historically isolated population in northwest Colombia. Linkage and haplotype analyses indicate that BPES in these families is linked to 3q23. Mutation screening of FOXL2 in the family with BPES type 1 revealed a novel 394C --> T nonsense mutation which deletes the forkhead DNA binding domain. The two families with BPES type 2 both carry an in-frame 30 bp duplication that leads to the elongation of a polyalanine tract. This duplication has been previously reported in Europe, where recurrent mutation has been demonstrated in unrelated familial and sporadic BPES cases. The recurrent nature of this duplication seems to relate to the secondary structure of this DNA region. The genotype-phenotype correlation seen in the Colombian families is consistent with the recent proposal that BPES type 1 is caused by truncating mutations leading to haploinsufficiency, while BPES type 2 is due to mutations generating elongated protein products.

Blepharophimosis↗

PubMed2003

FOXL2-mutations in blepharophimosis-ptosis-epicanthus inversus syndrome (BPES); challenges for genetic counseling in female patients.

Mutations in the forkhead transcription factor gene 2 (FOXL2) were recently reported to cause blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) types I and II. Evidence was provided that BPES type I (eyelid abnormalities and female infertility) is caused by mutations resulting in a truncated FOXL2 protein. In contrast, mutant FOXL2 proteins, either with inserted aminoacids in the forkhead domain or polyalanine tract, or with novel aminoacids at the carboxyl end, were found in BPES type II, in which fertility is generally normal. We report a 32-year-old female patient with sporadic BPES and a history of menstrual cycle irregularities and periods of secondary amenorrhoea. A heterozygous frameshift mutation (c959-960insG) was found in the FOXL2 gene, resulting in a predicted FOXL2 protein with 212 novel aminoacids in the carboxyl end, suggesting BPES type II despite menstrual irregularities. The clinical presentations of our patient and of three female patients with BPES type II in the report of De Baere et al. [2001: Hum Mol Genet 10:1591-1600.] indicate phenotypic overlap between BPES type I and II. These observations do not support a clear-cut prediction of female fertility based on the FOXL2 molecular defect. As a consequence, FOXL2 mutation testing in female patients of child-bearing age with BPES should be handled with caution, and a two-step genetic counseling approach, including an initial pre-test information session, is proposed.

Abnormalities, Multiple↗

PubMed2005

Interstitial deletion in 3q in a patient with blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) and microcephaly, mild mental retardation and growth delay: clinical report and review of the literature.

We present a boy with blepharophimosis, ptosis, epicanthus inversus, microcephaly, mild mental retardation, and growth delay. Chromosomal analysis revealed a male karyotype with an interstitial deletion in the long arm of chromosome 3. DNA-analysis showed that the deletion is of maternal origin and encompasses the region between markers D3S1535 and D3S1593. The deletion contains not only the FOXL2 gene, but also the gene encoding ataxia-telangiectasia and Rad3-related protein (ATR). Mutations in FOXL2 have been shown to cause blepharophimosis-ptosis-epicanthus inversus syndrome (BPES). ATR has been identified as a candidate gene for Seckel syndrome, an autosomal recessive syndrome that comprises growth retardation, microcephaly, and mental retardation. We hypothesize that our patient has a contiguous gene syndrome and that the non-BPES-associated abnormalities (microcephaly, mild mental retardation, and growth delay) are the result of the deletion of the maternal ATR gene. However, it has not yet been excluded that haploinsufficiency of some other gene in this region plays a role.

Abnormalities, Multiple↗

PubMed2003

Comparative analysis of the FOXL2 gene and characterization of mutations in BPES patients.

Bleparophimosis ptosis epicanthus inversus syndrome (BPES) is a rare disorder characterized by eyelid malformation and in some cases associated with premature ovarian failure. Although the familial form is autosomal dominant, many cases are also sporadic. The mutations causing this disorder were found in a winged/forkhead transcription factor gene named FOXL2. We have sequenced the mouse homolog for the FOXL2 gene and identified the Fugu rubripes (pufferfish) ortholog from the database. By alignment of the three sequences, we found an almost complete conservation of the forkhead domain in the three species. There is 95% and 61% conservation at the protein level between human-mouse and human-pufferfish, respectively. The polyalanine and polyproline tracts within the gene are absent in Fugu rubripes. An overview identifies four breaks in the conservation of the gene within these species. Using a direct sequencing approach, we performed mutation analysis from DNA of nine affected individuals from familial and sporadic cases. The mutations are distributed throughout the coding region of the FOXL2 gene. We identified five novel mutations: g.292delG (E19fsX149); g.530G>A (W98X); g.548A>G (H104R); g.652G>T (E139X); and g.1178_1185del8 (A314fsX530). In addition we also identified two known mutations g.823C>T (Q196X) and g.1092_1108dup17, the latter in individuals from three unrelated pedigrees.

Abnormalities, Multiple↗

PubMed2004

The human FOXL2 mutation database.

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES; MIM# 110100) is an autosomal dominant genetic condition in which an eyelid malformation is associated (type I) or not associated (type II) with premature ovarian failure (POF). In 2001, mutations in the FOXL2 gene, encoding a forkhead transcription factor, were shown to cause both BPES type I and II. Since then, a number of reports have appeared that describe intragenic FOXL2 mutations in BPES patients. In addition, a few FOXL2 variants have been reported in isolated POF patients and XX males. Previously, our group has described a large number of FOXL2 mutations, thereby demonstrating the existence of two mutational hotspots in FOXL2, intra- and interfamilial phenotypic variability in BPES families, and genotype-phenotype correlations for a number of mutations in BPES patients. Here we describe a locus-specific Human FOXL2 Mutation Database (http://medgen.ugent.be/foxl2/), created using the MuStaR software. Our database contains general information about the FOXL2 gene, as well as details about 135 intragenic mutations and variants of FOXL2, obtained from published papers, abstracts of meetings, and from unpublished data produced by our group. Not included in the current version of the database are variants residing outside the coding region of FOXL2 and molecular cytogenetic rearrangements of the FOXL2 locus. The Human FOXL2 Mutation Database was created to provide a unique publicly available online resource of information about human FOXL2 mutations/variants associated with BPES and POF. It allows remote users to submit new mutations to the database and to query the database using a web form. It will facilitate evaluation of the pathogenicity of a particular mutation, as it contains data about disease-causing mutations and polymorphisms in BPES and isolated POF patients, and a link to the known FOXL2 orthologs. Moreover, it will allow us to establish more accurate genotype-phenotype correlations, since clinical information is contained in the database.

Alleles↗

PubMed2006

Genetics of early mammalian folliculogenesis.

Early ovarian folliculogenesis begins with the breakdown of germ cell clusters and formation of primordial follicles. Primordial follicles are the smallest ovarian follicle units continuously recruited to grow into primary and more advanced ovarian follicles. Genes expressed in the germ cells such as Figla, Nobox, Kit and Ntrk2, as well as genes expressed in the surrounding somatic cells such as Foxl2, Kitl and Ngf, play critical functions during early folliculogenesis. Transgenic mice continue to provide important insights into the genetic pathways that regulate early mammalian folliculogenesis. Genes critical in early folliculogenesis are important determinants of reproductive life span and represent candidate genes for human ovarian failure.

Animals↗

PubMed2006

A novel polyalanine expansion in FOXL2: the first evidence for a recessive form of the blepharophimosis syndrome (BPES) associated with ovarian dysfunction.

The blepharophimosis syndrome (BPES) is an autosomal dominant developmental disorder in which craniofacial/eyelid malformations are associated (type I) or not (type II) with premature ovarian failure (POF). Mutations in the FOXL2 gene, encoding a forkhead transcription factor, are responsible for both types of BPES. Heterozygous polyalanine expansions of +10 residues (FOXL2-Ala24) account for 30% of FOXL2 mutations and are fully penetrant for the eyelid phenotype. Here we describe the first homozygous FOXL2 mutation leading to a polyalanine expansion of +5 residues (FOXL2-Ala19). This novel mutation segregates in an Indian family where heterozygous mutation carriers are unaffected whereas homozygous individuals have the typical BPES phenotype, with proven POF in one female. Expression of the FOXL2-Ala19 protein in COS-7 cells revealed a significantly higher cytoplasmic retention compared to the wild-type protein. This is the first study providing genetic evidence for a recessive inheritance of BPES associated with ovarian dysfunction.

Adult↗

PubMed2001

Heterozygous 17-bp deletion in the forkhead transcription factor gene, FOXL2, in a Japanese family with blepharophimosis-ptosis-epicanthus inversus syndrome.

We examined mutations in the forkhead transcription factor gene, FOXL2, in three members a Japanese family with autosomal dominant blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) and in 100 healthy controls. The FOXL2 was analyzed by direct genomic sequencing. A novel 17-bp deletion at nucleotides 1092-1108 in FOXL2 was found in the three affected patients. No mutation was found in any of the 100 healthy controls. The 17-bp deletion in FOXL2 may be involved in the pathogenesis of BPES in Japanese patients.

Adult↗

PubMed2005

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.

Animals↗

PubMed2006

Blepharophimosis, ptosis, and epicanthus inversus syndrome: clinical and molecular analysis of a case.

Blepharophimosis-ptosis-epicanthus inversus syndrome (OMIM #U10100) is a rare autosomal-dominant disorder in which an eyelid malformation is associated (type I) or not (type H) with premature ovarian failure in the affected female. It is invariably characterized by 4 major features: (1) bilaterally shortened horizontal palpebral fissure (blepharophimosis); (2) severe impairment of the superior palpebral levator (ptosis); (3) a vertical skin fold arising from the lower eyelid, which inserts medially in the upper lid (epicanthus inversus) and (4) an increased inner can-thal distance with a normal outer canthal distance (telecanthus). The mutations causing this disorder are found in the FOXL2 gene, a forkhead transcription factor, located in 3q23. Although many patients with blepharophimosis-ptosis-epicanthus inversus syndrome have an affected parent, a conspicuous number of sporadic cases also have been reported. We describe here a sporadic case with a mutation in the FOXL2 gene that was well characterized both clinically and molecularly.

Adult↗

PubMed2004

A novel insertion mutation in the FOXL2 gene is detected in a big Chinese family with blepharophimosis-ptosis-epicanthus inversus.

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES), an autosomal dominant syndrome in which an eyelid malformation is associated (type I) or not (type II) with premature ovarian failure (POF), has recently been ascribed to mutations in the forkhead transcription factor 2 (FOXL2) gene. In this work, we reveal a novel insertion mutation in the 3'UTR of the FOXL2 gene in a big Chinese family which is to our knowledge the first BPES (type II) family reported in China. It is the first time that a 3'UTR mutation in the FOXL2 gene has ever been found to demonstrate a close correlation between genotype and BPES. Our result gains a greater insight into the function of 3'UTR in the FOXL2 gene.

Base Sequence↗

PubMed2005

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.

Animals↗

PubMed2004

FOXL2 inactivation by a translocation 171 kb away: analysis of 500 kb of chromosome 3 for candidate long-range regulatory sequences.

A translocation breakpoint 171 kb 5' of the transcription start of FOXL2 causes blepharophimosis/ptosis/epicanthus inversus syndrome (BPES) and associated premature ovarian failure. The breakpoint falls within another gene, MRPS22, that has been sequenced in 500 kb of continuous DNA. MRPS22 encodes 20 exons and a number of alternative transcripts. Three CpG islands (>91% identical) are followed by noncoding exons 4-12 and coding exons 13-20. The 3'UTR extends into the 3'UTR of COPB2. Based on the sequence, three reported translocations that cause BPES all fall within intron 6 of MRPS22. Comparisons reveal conserved segments in introns 6, 11, and 12 of human and mouse. Notably intron 11 sequence is also deleted in goat PIS syndrome (which combines craniofacial defects, female infertility, and XX sex reversal). The conserved sequences are candidates for models in which they are distant enhancers or otherwise affect higher order chromatin structure to impose long-range cis regulation of FOXL2 expression.

Animals↗

PubMed2005

Sense and antisense Foxl2 transcripts in mouse.

FOXL2 is a forkhead transcription factor involved in eyelid development and in the development and adult function of the ovary in mammals. In mouse, we have previously suggested the existence of two mRNA isoforms of Foxl2 that result from an alternative polyadenylation. In this study, we characterize in depth the structure and expression of these two variants. We also describe an antisense transcript that overlaps the whole Foxl2 transcription unit. This antisense transcript, called Foxl2OS (for opposite strand), yields several isoforms resulting from alternative splicing. No significant coding region was found in the Foxl2OS sequence. Foxl2OS displays a pattern of expression very similar to that of Foxl2 in the gonads during development and at the adult age. RNA FISH experiments show that both transcripts are expressed in the same cells at the same time. We suggest that Foxl2OS is a noncoding antisense RNA that may be involved in the regulation of Foxl2. All in all our results provide new insights about the organization of the murine Foxl2 locus. This might help us understand its regulation and function.

Alternative Splicing↗

PubMed2005

Ovarian-specific expression of a new gene regulated by the goat PIS region and transcribed by a FOXL2 bidirectional promoter.

Studies on XX sex reversal in polled goats (PIS mutation: polled intersex syndrome) have led to the discovery of a female-specific locus crucial for ovarian differentiation. This genomic region is composed of at least two genes, FOXL2 and PISRT1, sharing a common transcriptional regulatory region, PIS. In this paper, we describe a third gene, PFOXic (promoter FOXL2 inverse complementary), located near FOXL2 in the opposite orientation. This gene composed of five exons encodes a 1723-bp cDNA, enclosing two repetitive elements in its 3' end. PFOXic mRNA encodes a putative protein of 163 amino acids with no homologies in any of the databases tested. The transcriptional expression of PFOXic is driven by a bidirectional promoter also enhancing FOXL2 transcription. In goats, PFOXic is expressed in developing ovaries, from 36 days postcoitum until adulthood. Ovarian-specific expression of PFOXic is regulated by the PIS region. PFOXic is found conserved only in Bovidae. But, a human gene located in the opposite orientation relative to FOXL2 can be considered a human PFOXic. Finally, we discuss evidence arguing for regulation of the level of FOXL2 transcription via the bidirectional promoter and the level of transcription of PFOXic.

Animals↗

PubMed2006

Reverse transcriptase template switching and false alternative transcripts.

Reverse transcriptase (RT) can switch from one template to another in a homology-dependent manner. In the study of eukaryotic transcripts, this propensity of RT can produce an artificially deleted cDNA, which can be wrongly interpreted as an alternative transcript. Here, we have investigated the presence of such template-switching artifacts in cDNA databases, by scanning a collection of human splice sites (Information for the Coordinates of Exons, ICE database). We have confirmed several cases at the experimental level. Artifacts represent a significant portion of apparently spliced sequences using noncanonical splice signals but are rare in the context of the whole database. However, care should be taken in the annotation of alternative transcripts, especially when the RT used is poorly thermostable and when the putative intron is flanked by direct repeats, which are the substrate for template switching.

Alternative Splicing↗