Balkan Journal of Medical Genetics

CHROMOSOMAL POLYMORPHISMS INVOLVED IN REPRODUCTIVE FAILURE IN THE ROMANIAN POPULATION
Mierla D1,2*, Stoian V2
*Corresponding Author: Dana Mierla MD, Department of Genetics, Faculty of Biology, University of Bucharest, Bucharest, Romania; Tel.: +40721479083; E-mail: dana_mierla@yahoo.com
page: 23

INTRODUCTION

Infertility is a significant marital problem, affecting up to 15.0% of couples of reproductive age [1,2]. Infertility can be caused by defects in the development of the urogenital system or defects in function of the endocrine system, including the hypothalamicpituitary- gonadal axis, or by defects in gametogenesis, sexual function, fertilization or early embryonic development [3]. Secondary or acquired infertility, such as after tubal diseases, vasectomy or exposure to gonadotoxins may also occur [4]. Genetic pathology is an increasingly important part of general human pathology as the number of described genetic diseases and their frequency increases. Study of human chromosomes play a key role in diagnosis, prognosis, treatment and monitoring of chromosomal abnormalities. In order to provide genetical counseling for affected families, cytogenetic analysis is the crucial investigation. Several studies have been published regarding chromosome analysis in couples with reproductive failure who are referred for IVF (in vitro fertilization) or other treatments [5]. The incidence of chromosomal abnormalities in people with infertility appears to be greater than the overall incidence of chromosomal abnormalities in the general population [6]. It is unclear whether chromosomal abnormalities are one of the main causes of infertility in the human population. Many researchers believe that there is an association between genetic abnormalities and infertility in both men and women [7,8]. Approximately 40.0% of infertility cases are due to male pathology, 40.0% to female pathology, and the remaining 20.0% is a combination of the two [8]. About 5.0% of infertile men have chromosomal abnormalities, most of which involve sex chromosomes. Chromosomal abnormalities are a major cause of male and female infertility and can be defined as an alteration of function and structure of chromosomes [9]. Cytogenetic abnormalities, both acquired and inherited, are one of the most common genetic causes of miscarriages early in pregnancies [10]. Most chromosomal abnormalities may cause a genetic imbalance that causes various phenotypic abnormalities (delayed growth and development, multiple congenital anomalies, disorders of sexuality and reproduction, etc.) due to partial trisomy or monosomy of the regions involved. Cytogenetic studies have been reported to determine the contribution of chromosomal abnormalities in patients with reproductive failure [11]. The purpose of the present study was to investigate the effects of chromosomal polymorphic variations involved in reproductive failure. Polymorphism variations mainly refer to the variants in the chromosomal heterochromatin region. To be classified as variants, chromosomal poly-morphisms needed to be at least twice the size of the corresponding region on the second homologous chromosome [2]. Polymorphic variants on non acrocentric chromosomes usually occur in the paracentric heterochromatin on the long arms of chromosomes 1, 9 and 16, the shortarm regions of the D and G group chromosomes, and the distal heterochromatin of the Y chromosome. Increased lengths of the heterochromatic regions on the long arms of these chromosomes are designated as 1qh+, 9qh+, 16qh+ and Yqh+. The heterochromatin can be reduced in these chromosomes, such as in the case of 1qh−, 9qh− and 16qh−. Increased lengths of the short-arm satellites of the acrocentric D and G group chromosomes (13, 14, 15, 21 and 22) are designated as 14ps+ and 13ps+, while increased lengths of the short arms themselves are designated as p+ (e.g., 15p+) [12]. Because the heterochromatic region consists of highly repeated sequences of satellite DNA that does not encode proteins, the chromosomal polymorphism variations are considered normal karyotypic variations [13]. However, many recent studies indicate that chromosomal polymorphisms may cause certain clinical effects, such as infertility and spontaneous miscarriage [12,14,15].

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