Functional Studies of Novel FOXL2 Variants in Chinese Families With Blepharophimosis-Ptosis-Epicanthus Inversus Syndrome

Novel FOXL2 variants in two Chinese families with blepharophimosis, ptosis, and epicanthus inversus syndrome

Introduction: Blepharophimosis, ptosis, and epicanthus inversus syndrome (BPES) is a rare inherited disorder. This study was aimed to identify and functionally validate FOXL2 variants in two Chinese families with BPES. Methods: The proband and his family members were subjected to whole-exome sequencing to identify disease-associated variants. Several bioinformatic tools were used to computationally predict altered proteins. In vitro functional assays were conducted by transfecting wild-type and mutant FOXL2 cDNAs into HEK-293 cells, followed by subcellular localization assays, luciferase reporter gene assays, and quantitative real-time polymerase chain reaction. Results: The clinical features of BPES, including small palpebral fissures, ptosis, telecanthus, and epicanthus inversus, were present in all affected patients. Two novel mutations were detected, c.292T>A and c.383G>T. Whole-exome sequencing analysis and prediction software suggested that these mutations were pathogenic. Functional studies showed that these two point mutations decreased FOXL2 protein expression, resulting in subcellular mislocalization and aberrant transcriptional activity of the steroidogenic acute regulatory protein gene promoter. Conclusion: Our results add to the current understanding of known FOXL2 variants in, and our in vitro experiments provide reference data and insights into the etiology of BPES. Further studies are needed to identify the possible mechanisms underlying the action of this mutation on the development of BPES.

Deletion of cis-regulatory Element in FOXL2 Promoter in a Chinese Family of Type II Blepharophimosis-ptosis-epicanthus Inversus Syndrome with Polydactyly

Blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) is a relatively uncommon autosomal-dominant genetic disorder, primarily attributed to mutations in the forkhead box L2 (FOXL2) gene. Albeit the involvement of protein-coding regions of FOXL2 has been observed in the majority of BPES cases, whether deficiencies in regulatory elements lead to the pathogenesis remains poorly understood. Herein, an autosomal-dominant BPES type II family was included. Peripheral venous blood has been collected, and genomic DNA has been extracted from leukocytes. A whole exome sequencing analysis has been performed and analyzed (Deposited in NODE database: OER422653). The promoter region of FOXL2 was amplified using polymerase chain reaction (PCR). The luciferase reporter assay was performed to identify the activity of this region. In this study, we present a Chinese family diagnosed with type II BPES, characterized by the presence of small palpebral fissures, ptosis, telecanthus, and epicanthus inversus. Notably, all male individuals within the family display polydactyly. A 225-bp deletion in the 556-bp 5'-upstream to transcription start site of FOXL2 , decorated by multiple histone modifications, was identified in affected members of the family. This deletion significantly decreased FOXL2 promoter activity, as measured by the luciferase assay. Conclusively, a novel 255-bp-deletion of the FOXL2 promoter was identified in Chinese families with BPES. Our results expand the spectrum of known FOXL2 mutations and provide additional insight into the genotype-phenotype relationships of the BPES pathogenesis. In addition, this study indicates the important role of genetic screening of cis-regulatory elements in testing heritable diseases.

Current understanding of the genomic abnormities in premature ovarian failure: chance for early diagnosis and management

Premature ovarian failure (POF) is an insidious cause of female infertility and a devastating condition for women. POF also has a strong familial and heterogeneous genetic background. Management of POF is complicated by the variable etiology and presentation, which are generally characterized by abnormal hormone levels, gene instability and ovarian dysgenesis. To date, abnormal regulation associated with POF has been found in a small number of genes, including autosomal and sex chromosomal genes in folliculogenesis, granulosa cells, and oocytes. Due to the complex genomic contributions, ascertaining the exact causative mechanisms has been challenging in POF, and many pathogenic genomic characteristics have yet to be elucidated. However, emerging research has provided new insights into genomic variation in POF as well as novel etiological factors, pathogenic mechanisms and therapeutic intervention approaches. Meanwhile, scattered studies of transcriptional regulation revealed that ovarian cell function also depends on specific biomarker gene expression, which can influence protein activities, thus causing POF. In this review, we summarized the latest research and issues related to the genomic basis for POF and focused on insights gained from their biological effects and pathogenic mechanisms in POF. The present integrated studies of genomic variants, gene expression and related protein abnormalities were structured to establish the role of etiological genes associated with POF. In addition, we describe the design of some ongoing clinical trials that may suggest safe, feasible and effective approaches to improve the diagnosis and therapy of POF, such as Filgrastim, goserelin, resveratrol, natural plant antitoxin, Kuntai capsule et al. Understanding the candidate genomic characteristics in POF is beneficial for the early diagnosis of POF and provides appropriate methods for prevention and drug treatment. Additional efforts to clarify the POF genetic background are necessary and are beneficial for researchers and clinicians regarding genetic counseling and clinical practice. Taken together, recent genomic explorations have shown great potential to elucidate POF management in women and are stepping from the bench to the bedside.

Selected Genetic Factors Associated with Primary Ovarian Insufficiency

Primary ovarian insufficiency (POI) is a heterogeneous disease resulting from non-functional ovaries in women before the age of 40. It is characterized by primary amenorrhea or secondary amenorrhea. As regards its etiology, although many POI cases are idiopathic, menopausal age is a heritable trait and genetic factors play an important role in all POI cases with known causes, accounting for approximately 20% to 25% of cases. This paper reviews the selected genetic causes implicated in POI and examines their pathogenic mechanisms to show the crucial role of genetic effects on POI. The genetic factors that can be found in POI cases include chromosomal abnormalities (e.g., X chromosomal aneuploidies, structural X chromosomal abnormalities, X-autosome translocations, and autosomal variations), single gene mutations (e.g., newborn ovary homeobox gene (NOBOX), folliculogenesis specific bHLH transcription factor (FIGLA), follicle-stimulating hormone receptor (FSHR), forkhead box L2 (FOXL2), bone morphogenetic protein 15 (BMP15), etc., as well as defects in mitochondrial functions and non-coding RNAs (small ncRNAs and long ncRNAs). These findings are beneficial for doctors to diagnose idiopathic POI cases and predict the risk of POI in women.

Ovarian Reserve and ART Outcomes in Blepharophimosis-Ptosis-Epicanthus Inversus Syndrome Patients With FOXL2 Mutations

Objective

To characterize the status of ovarian reserve and ART outcomes in BPES women and provide informative reference for clinical diagnosis and treatment.

Methods

Twenty-one women with BPES were screened for mutations in the FOXL2 gene and underwent assisted reproductive technology (ART) treatment. Indicators for ovarian reserve and ART outcomes were compared between patients with and without FOXL2 mutations. Additionally, ART outcomes were compared among patients with different subtypes of FOXL2 mutations.

Results

A total of 13 distinct heterozygous variants in the FOXL2 gene were identified in 80.95% of BPES women, including 4 novel mutations with plausible pathogenicity (c.173_175dup, c.481C>T, c.576del and c.675_714del). Compared to non-mutation group, patients with FOXL2 mutations had elevated levels of FSH (P=0.007), decreased AMH levels (P=0.012) and less AFC (P=0.015). They also had worse ART outcomes with large amount of Gn dosage (P=0.008), fewer oocytes (P=0.001), Day3 good quality embryos (P=0.001) and good quality blastocysts (P=0.037), and a higher cancellation rate (P=0.272). High heterogeneity of ART outcomes existed in BPES patients with different FOXL2 mutation types.

Conclusions

BPES patients with FOXL2 mutations had diminished ovarian reserve and adverse ART outcomes. The genotype-reproductive phenotype correlations were highly heterogeneous and cannot be generalized. Genetic counseling for fertility planning and preimplantation or prenatal genetic diagnosis to reduce offspring inheritance are recommended.