M.Sc Thesis

M.Sc StudentKoren Mordechai
SubjectDevelopment of a Comprehensive Approach to the Molecular
Diagnosis of Congenitial Recessive Ichthyosis
DepartmentDepartment of Biotechnology
Supervisors PROF. Eli Sprecher


Congenital recessive ichthyoses (CRI) are characterized by diffuse skin scaling and erythema. CRI has been mapped to at least 7 distinct chromosomal loci. Unfortunately, no practical screening method is yet available. I assessed 5 7 individuals belonging to 1 1 consanguineous kindreds with CRI, including 17 patients. I tested screening panels of the 7 loci previously shown to be associated with CRI on 2q33-p35, 3p21, 12q11-q13, 14q11.2, 17p13.2-13.1, 19p12-q12, 19p13.2-13.1. Given the fact that all studied families were consanguineous, I assumed the existence of founder (homozygous) causative mutations in each kindred. I therefore searched for regions of homozygosity in each family for each of the loci (homozygosity mapping). In the course of these studies, I identified a novel CRI-associated locus on 12q. I identified homozygous chromosomal disease-segregating regions in 10 out the 1 1 families, and identified by mutational analysis novel TGM1 mutations in those families that mapped to 14q11.2. I used PCR-RFLP and an enzymatic assay to validate our finding. I developed 3 fluorescently-labeled marker panels, significantly reducing the turnaround time of the diagnostic process. In sum, homozygosity mapping represents an efficient, inexpensive and rapid screening diagnostic approach in consanguineous families with CRI; it can be used to direct subsequent mutational analysis as well as serve in prenatal diagnosis. It is amenable to semi-automation and could be applicable to additional recessive disorders characterized by genetic heterogeneity. The present study emphasizes the usefulness in human genetics of diagnostic strategies tailored to the demographic features of target populations.