The Genetic and Genomic Landscape of Human Reproductive Disorders: An Overview with Our Experience

Abstract

Genetics and genomics play a role in the causation of various human diseases. A large number of human reproductive disorders also arise as a result of genetic and genomic abnormalities. Reproductive disorders associated with predominantly genetics and genomic abnormalities are infertility, early pregnancy loss, congenital malformations, difference or disorder of sex development and reproductive cancers. The genetic etiology of human reproductive disorders is increasing with improved molecular biology techniques such as DNA microarray and next-generation sequencing. Infertility is one of the significant areas of reproductive disorders where genetics/genomics plays a substantial role and may result from chromosomal, copy number variation, Yq & pseudo autosomal region microdeletion/microduplication, gene mutation (monogenic, oligogenic, polygenic), multifactorial, epigenetic, mitochondrial, etc. abnormalities. All idiopathic infertile couples should be screened for genetic disorders before assisted reproduction to prevent transmission, if any, in offspring. Pregnancy wastage in early pregnancy is very high (about 70%) and is mainly related to chromosome number, copy number variation, and some monogenic or epigenetic abnormalities. Therefore, all early pregnancy loss cases should also be tested for genetic causes. Congenital malformations are structural defects in embryo, fetus, or newborns and affect about 3% (major malformations) of all births. The malformations could be due to the abnormalities of chromosomes, copy number variation, monogenic, oligogenic, multifactorial, or environmental. Array CGH &/or NGS should be used as the first step to screen congenital malformations. Differences/disorder of sex development is a developmental defect in which the determination and/or differentiation of chromosomal, gonadal, or phenotypic/anatomic sex is abnormal. It is a common disorder and is primarily related to genetic abnormalities. Therefore, a precise diagnosis, mainly through an array CGH and/or NGS, is crucial for the proper management to prevent future psychosexual problems and another birth with the disorder. Cancer is a genomic disorder characterized by genomic instability (due to a defect in DNA repair mechanism), uncontrolled replication (due to lack of response to inhibitory factors/loss of contact inhibition), neo-angiogenesis, invasion and metastasis. All cancer cases should be investigated for genomic markers (both hereditary and somatic) for precise diagnosis, prognosis, and genetic counseling. In this review, we will try to evaluate the role of genetics and genomics in the above-mentioned reproductive disorders, along with genetic & genomic techniques used and reproductive counseling in addition to our experiences.