A novel TLE6 mutation, c.541+1G>A, identified using whole-exome sequencing in a Chinese family with female infertility

Advances in the genetic etiology of female infertility

Human reproduction is a complex process involving gamete maturation, fertilization, embryo cleavage and development, blastocyst formation, implantation, and live birth. If any of these processes are abnormal or arrest, reproductive failure will occur. Infertility is a state of reproductive dysfunction caused by various factors. Advances in molecular genetics, including cell and molecular genetics, and high-throughput sequencing technologies, have found that genetic factors are important causes of infertility. Genetic variants have been identified in infertile women or men and can cause gamete maturation arrest, poor quality gametes, fertilization failure, and embryonic developmental arrest during assisted reproduction technology (ART), and thus reduce the clinical success rates of ART. This article reviews clinical studies on repeated in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) failures caused by ovarian dysfunction, oocyte maturation defects, oocyte abnormalities, fertilization disorders, and preimplantation embryonic development arrest due to female genetic etiology, the accumulation of pathogenic genes and gene pathogenic loci, and the functional mechanism and clinical significance of pathogenic genes in gametogenesis and early embryonic development.

Roles of transducin-like enhancer of split (TLE) family proteins in tumorigenesis and immune regulation

Mammalian transducin-like enhancer of split family proteins (TLEs) are homologous to Drosophila Groucho (Gro) and are essential transcriptional repressors. Seven TLE family members, TLE1-7, have been identified to date. These proteins do not bind DNA directly; instead, they bind a set of transcription factors and thereby inhibit target gene expression. Loss of TLEs in mice usually leads to defective early development; however, TLE functions in developmentally mature cells are unclear. Recent studies have revealed that TLEs are dysregulated in certain human cancer types and may function as oncogenes or tumor suppressors in different contexts. TLE levels also affect the efficacy of cancer treatments and the development of drug resistance. In addition, TLEs play critical roles in the development and function of immune cells, including macrophages and lymphocytes. In this review, we provide updates on the expression, function, and mechanism of TLEs; discuss the roles played by TLEs in tumorigenesis and the inflammatory response; and elaborate on several TLE-associated signaling pathways, including the Notch, Wnt, and MAPK pathways. Finally, we discuss potential strategies for targeting TLEs in cancer therapy.

Molecular tools for the genomic assessment of oocyte’s reproductive competence

The most important factor associated with oocytes' developmental competence has been widely identified as the presence of chromosomal abnormalities. However, growing application of genome-wide sequencing (GS) in population diagnostics has enabled the identification of multifactorial genetic predispositions to sub-lethal pathologies, including those affecting IVF outcomes and reproductive fitness. Indeed, GS analysis in families with history of isolated infertility has recently led to the discovery of new genes and variants involved in specific human infertility endophenotypes that impact the availability and the functionality of female gametes by altering unique mechanisms necessary for oocyte maturation and early embryo development. Ongoing advancements in analytical and bioinformatic pipelines for the study of the genetic determinants of oocyte competence may provide the biological evidence required not only for improving the diagnosis of isolated female infertility but also for the development of novel preventive and therapeutic approaches for reproductive failure. Here, we provide an updated discussion and review of the progresses made in preconception genomic medicine in the identification of genetic factors associated with oocyte availability, function, and competence.

Gene mutations associated with fertilization failure after in vitro fertilization/intracytoplasmic sperm injection

Fertilization failure during assisted reproductive technologies (ART) is often unpredictable, as this failure is encountered only after in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) have been performed. The etiology of fertilization failure remains elusive. More and more mutations of genes are found to be involved in human fertilization failure in infertile patients as high throughput sequencing techniques are becoming widely applied. In this review, the mutations of nine important genes expressed in sperm or oocytes, PLCZ1, ACTL7A, ACTL9, DNAH17, WEE2, TUBB8, NLRP5, ZP2, and TLE6, were summarized and discussed. These abnormalities mainly have shown Mendelian patterns of inheritance, including dominant and recessive inheritance, although de novo mutations were present in some cases. The review revealed the crucial roles of each reported gene in the fertilization process and summarized all known mutations and their corresponding phenotypes. The review suggested the mutations might become promising targets for precision treatments in reproductive medicine. Moreover, our work will provide some helpful clues for genetic counseling, risk prediction, and optimizing clinical treatments for human infertility by supplying the useful and timely information on the genetic causes leading to fertilization failure.

A novel TLE6 mutation, c.541+1G>A, identified using whole-exome sequencing in a Chinese family with female infertility

Background

Oocytes have a lot of maternal RNAs and proteins, which are used by the early embryo before zygotic genome activation. Transducin‐like enhancer of split 6 (TLE6) is a component of a subcortical maternal complex which plays a critical role in early embryonic development.

Methods

The patient had been diagnosed with primary infertility for 6 years and had undergone multiple failed in vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) cycles. Genomic DNA samples were extracted from her parents’ peripheral blood as well as hers. Whole‐exome sequencing and Sanger validation were performed to identify candidate variants.

Results

We identified a novel transducin‐like enhancer of split 6 (TLE6) gene mutations in the female patient with recurrent IVF/ICSI failure. The patient carried a homozygous mutation (NM_001143986.1(TLE6): c.541+1G>A) and had viable but low‐quality embryos. Her parents both had heterozygous mutations at this locus.

Conclusion

Our study expands the mutational and phenotypic spectrum of TLE6 and suggests the important role of TLE6 during embryonic development. Our findings have implications for the genetic diagnosis of female infertility with recurrent IVF/ICSI failure.