A genome-wide screen for copy number alterations in an adolescent pilot cohort with müllerian anomalies

Molecular Basis of Müllerian Agenesis Causing Congenital Uterine Factor Infertility-A Systematic Review

Infertility affects around 1 in 5 couples in the world. Congenital absence of the uterus results in absolute infertility in females. Müllerian agenesis is the nondevelopment of the uterus. Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a condition of uterovaginal agenesis in the presence of normal ovaries and the 46 XX Karyotype. With advancements in reproductive techniques, women with MA having biological offspring is possible. The exact etiology of MA is unknown, although several genes and mechanisms affect the development of Müllerian ducts. Through this systematic review of the available literature, we searched for the genetic basis of MA. The aims included identification of the genes, chromosomal locations, changes responsible for MA, and fertility options, in order to offer proper management and counseling to these women with MA. A total of 85 studies were identified through searches. Most of the studies identified multiple genes at various locations, although the commonest involved chromosomes 1, 17, and 22. There is also conflicting evidence of the involvement of various candidate genes in the studies. The etiology of MA seems to be multifactorial and complex, involving multiple genes and mechanisms including various mutations and mosaicism.

Identification of Genetic Causes in Mayer-Rokitansky-Küster-Hauser (MRKH) Syndrome: A Systematic Review of the Literature

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a congenital condition characterizing females with absence of the uterus and part of the vagina. Several genetic defects have been correlated with the presence of MRKH; however, the exact etiology is still unknown due to the complexity of the genetic pathways implicated during the embryogenetic development of the Müllerian ducts. A systematic review (SR) of the literature was conducted to investigate the genetic causes associated with MRKH syndrome and Congenital Uterine Anomalies (CUAs). This study aimed to identify the most affected chromosomal areas and genes along with their associated clinical features in order to aid clinicians in distinguishing and identifying the possible genetic cause in each patient offering better genetic counseling. We identified 76 studies describing multiple genetic defects potentially contributing to the pathogenetic mechanism of MRKH syndrome. The most reported chromosomal regions and the possible genes implicated were: 1q21.1 (RBM8A gene), 1p31-1p35 (WNT4 gene), 7p15.3 (HOXA gene), 16p11 (TBX6 gene), 17q12 (LHX1 and HNF1B genes), 22q11.21, and Xp22. Although the etiology of MRKH syndrome is complex, associated clinical features can aid in the identification of a specific genetic defect.

Bi-allelic truncating variants in CFAP206 cause male infertility in human and mouse

Spermatozoa are polarized cells with a head and a flagellum joined together by the connecting piece. Flagellum integrity is critical for normal sperm function, and flagellum defects consistently lead to male infertility. Multiple morphological abnormalities of the flagella (MMAF) is a distinct sperm phenotype consistently leading to male infertility due to a reduced or absent sperm motility associated with severe morphological and ultrastructural flagellum defects. Despite numerous genes recently described to be recurrently associated with MMAF, more than half of the cases analyzed remain unresolved, suggesting that many yet uncharacterized gene defects account for this phenotype. By performing a retrospective exome analysis of the unsolved cases from our initial cohort of 167 infertile men with a MMAF phenotype, we identified one individual carrying a homozygous frameshift variant in CFAP206, a gene encoding a microtubule-docking adapter for radial spoke and inner dynein arm. Immunostaining experiments in the patient's sperm cells demonstrated the absence of WDR66 and RSPH1 proteins suggesting severe radial spokes and calmodulin and spoke-associated complex defects. Using the CRISPR-Cas9 technique, we generated homozygous Cfap206 knockout (KO) mice which presented with male infertility due to functional, structural and ultrastructural sperm flagellum defects associated with a very low rate of embryo development using ICSI. Overall, we showed that CFAP206 is essential for normal sperm flagellum structure and function in human and mouse and that bi-allelic mutations in CFAP206 cause male infertility in man and mouse by inducing morphological and functional defects of the sperm flagellum that may also cause ICSI failures.

Identification of Candidate Genes for Mayer-Rokitansky-Küster-Hauser Syndrome Using Genomic Approaches

Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome is a disorder of sex development which affects 1 in 4,500 females and is characterized by agenesis of müllerian structures, including the uterus, cervix, and upper vagina. It can occur in isolation (type 1) or in conjunction with various anomalies (type 2), with a subset of these comprising müllerian, renal, and cervicothoracic abnormalities (MURCS) association. The genetic causes of MRKH have been investigated previously yielding limited results, with massive parallel sequencing becoming increasingly utilized. We sought to identify genetic contributions to MRKH using a combination of microarray and whole exome sequencing (WES) on a cohort of 8 unrelated women with MRKH and MURCS. WES data were analysed using a candidate gene approach to identify potential contributing variants. Microarray analysis identified a 0.6-Mb deletion in the previously implicated 16p11.2 region in a patient with MRKH type 2. WES revealed 16 rare nonsynonymous variants in MRKH candidate genes across the cohort. These included variants in several genes, such as LRP10 and DOCK4, associated with disorders with müllerian anomalies. Further functional studies of these variants will help to delineate their biological significance and expand the genotypic spectrum of MRKH.

Concurrent exome-targeted next-generation sequencing and single nucleotide polymorphism array to identify the causative genetic aberrations of isolated Mayer-Rokitansky-Küster-Hauser syndrome

STUDY QUESTION

Can the use of whole-exome sequencing (WES) together with single nucleotide polymorphism (SNP) array help to identify novel causative genes of isolated Mayer-Rokitansky-Küster-Hauser (MRKH) syndrome?

SUMMARY ANSWER

OR4M2 (olfactory receptor, family 4, subfamily M, member 2) and PDE11A (phosphodiesterase 11A) gene loss-of-function variants as well as deletions at 15q11.2, 19q13.31, 1p36.21, and 1q44 were identified as possible commonly altered regions in patients with type 1 MRKH.

WHAT IS KNOWN ALREADY

The isolated form of Müllerian aplasia is the most common subtype of MRKH syndrome, which invariably leads to difficulties producing offspring in affected women. However, there is little information currently available to allow for genetic testing and counseling to be performed for those affected by this syndrome.

STUDY DESIGN, SIZE AND DURATION

This was a case-series genetic study. A total of seven consecutive unrelated women with type 1 MRKH were enrolled. The enrollment and experimental procedures were performed over a 2-year period.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Whole exome-targeted next-generation sequencing and SNP array (Affymetrix Genome-Wide Human SNP Array 6.0) were performed on the first five unrelated women with type 1 MRKH syndrome. The data were combined, and the '3-hit principal' was applied on a genome-wide scale to search for the common causative genes. Quantitative PCR (qPCR) and Sanger sequencing were used to validate the identified genomic copy number losses and variants. Replication tests using direct Sanger sequencing and qPCR were performed on the remaining two women with type 1 MRKH syndrome to support the credibility of the potential candidate genes and deletions.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 3443 damaging variants based on WES were shown to intersect with 1336 copy number variations (deletions) derived from the SNP array. Four highly recurrent deletions at 15q11.2 (80%), 19q13.31 (40%), 1p36.21 (40%) and 1q44 (40%) were identified in the first five women with type 1 MRKH syndrome and were considered to be novel candidate aberrations. A previously reported 1q21.1 deletion was also recurrent in two of the first five women with type 1 MRKH syndrome. The 1q44 and 19q13.31 deletions were present in at least one of the two additional patients. Damaging variants were detected in HNRNPCL1 (heterogeneous nuclear ribonucleoprotein C-like 1), OR2T2 (olfactory receptor, family 2, subfamily T, member 2), OR4M2, ZNF816 (zinc finger protein 816), and PDE11A in several of the initial five patients. Among these, the damaging variants of OR4M2 (located at 15q11.2) and PDE11A were found in at least one of the two additional patients with type 1 MRKH.

LIMITATIONS, REASONS FOR CAUTION

In this study, we only searched for the deletions or damaging variants causing loss-of-function of genes in at least three of the initial five patients (3-hit criteria). Therefore, the study was designed to only detect common causative genes. Genomic duplications and/or rare individual mutations that may have also contributed to MRKH syndrome were not investigated.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrated the feasibility of the use of combined data from both WES and SNP arrays for the identification of possible common causative genetic aberrations in patients with type 1 MRKH syndrome on a genome-wide scale. Further validation of our found causative genes is required before applying on genetic testing and counseling.

STUDY FUNDING/COMPETING INTERESTS

The study was supported by grants from the National Science Council of Taiwan (NSC98-2314-B002-105-MY3 and NSC 100-2314-B002-027-MY3). The funding sources had no involvement in the design or analysis of the study. The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

Not applicable.