overview of mutation detection methods in genetic disorders

Genetic disorders are traditionally categorized into three main groups: single-gene, chromosomal, and multifactorial disorders. Single gene or Mendelian disorders result from errors in DNA sequence of a gene and include autosomal dominant [AD], autosomal recessive [AR], X-linked recessive [XR], X-linked dominant and Y-linked [holandric] disorders. Chromosomal disorders are due to chromosomal aberrations including numerical and structural damages. Molecular and cytogenetic techniques have been applied to identify genetic mutations leading to diseases. Accurate diagnosis of diseases is essential for appropriate treatment of patients, genetic counseling and prevention strategies. Characteristic features of patterns of inheritance are briefly reviewed and a short description of chromosomal disorders is also presented. In addition, applications of cytogenetic and molecular techniques and different types of mutations are discussed for genetic diagnosis of the pediatric genetic diseases. The purpose is to make pediatricians familiar with the applications of cytogenetic and molecular techniques and tools used for genetic diagnosis

Molecular diagnosis of congenital adrenal hyperplasia in Iran: focusing on CYP21A2 gene

Congenital adrenal hyperplasia [CAH] is characterized by impaired biosynthesis of cortisol. 21-hydroxylase deficiency is the most common cause of CAH affecting 1 in 10000-15000 live births over the world. The frequency of the disorder is very high in Iran due to frequent consanguineous marriages. Although biochemical tests are used to confirm the clinical diagnosis, molecular methods could help to define accurate diagnosis of the genetic defect. Recent molecular approaches such as polymerase chain reaction based methods could be used to detect carriers and identify different genotypes of the affected individuals in Iran which may cause variable degrees of clinical expression of the condition. Molecular tests are also applied for prenatal diagnosis, and genetic counseling of the affected families. Here, we are willing to delineate mechanisms underlying the disease, genetic causes of CAH, genetic approaches being used in the country and recommendations for health care improvement on the basis of the molecular and clinical genetics to control and diminish such a high prevalent disorder in Iran. Also, the previous studies on CAH in Iran are gathered and a diagnostic algorithm for the genetic causes is proposed

[Investigation of connexin 26 mutations and three large deletions spanning connexin 30 in 63 Iranian families with autosomal recessive non-syndromic hearing loss]

Hearing loss is the most frequent neurosensory defect in human. Mutations in GJB2 and GJB6 are responsible for 50% of autosomal recessive non-syndromic hearing loss [ARNSHL] cases. Here we report on the frequencies of GJB2 and GJB6 mutations and three large deletions spanning the GJB6 gene including Del [GJB6-D13S1830], Del [GJB6-D13S1854] and a>920 kb deletion in patients affected by ARNSHL referred to Kawsar's Human Genetics Research Center. In this study, 94 patients from 63 families with ARNSHL were investigated. Patient's homozygote for 35delG were screened and left out of the study and the remaining samples were analyzed by sequencing of GJB2 and GJB6 genes. Also the three large deletions spanning the GJB6 gene were analyzed by Real Time PCR In this study we found GJB2 mutations in 13 families [20.6%] out of 63.The 35delG mutation was the most common mutation in the studied population [61.5%]. Other GJB2 mutations were delE120, R127H, W24X, and V37I. The heterozygous or negative cases for the GJB2 mutations were screened for mutation in the GJB6 gene by sequencing and no mutation was observed. Also, we checked the three large deletions in GJB6, we found no mutations. Low frequency of mutations in the GJB2 gene implies that other genes may be involved in causing non-syndromic hearing loss in our country

Sister chromatid exchange in peripheral blood lymphocytes as a possible breast cancer risk biomarker: a study of Iranian patients with breast cancer

Sister chromatid exchanges [SCEs] can be induced by various genotoxic treatments, suggesting that SCEs reflect a DNA repair process and it may be a good index for assessment of genomic instability. However, the occurrence of genetic instability and in particular, of spontaneous SCEs has been strongly linked to cancer. Several chromosomal regions and many genes have been implicated in breast cancer. Blood samples were obtained from 31 Iranian breast cancer patients and 11 healthy women. SCE was measured in peripheral blood lymphocytes by adding to Ham'sF10 medium in presence of PHA, BrdU [5-bromo-deoxy Uridine] fluorochrome Hoechst 33258, exposure to UV light and Giemsa staining. Then, SCE frequencies of patient and control groups were compared by the Mann-Withney U-test. Significantly difference was observed between two groups [p < 0.001]. This study indicates that SCE can be used as a risk biomarker for breast cancer