Family A belongsto Village Manga, District Mardan, Khyber Pakhtunkhwa province. The family membersare engaged in regular farming and cattle herding. Inter marriages are a commonpractice here which results in genetic disorders. The pedegree drawingpresented in Figureindicate four generations with 2 affected males (IV-1 and IV-2) and 2 affectedfemale (IV-5 and IV6) individuals. Consanguineous marriage has been shown in the pedigree in3rd generation and the disease appeared in 4th generation.The pedigree analysis shows that affected individuals were produced byunaffected parents and the affected status was independent of the sexsuggesting that the trait is transmitted in autosomal recessive manner. Pedigree analysis strongly suggeststhe autosomal recessive mode of inheritance.
Autosomal recessive primary microcephaly is congenital inall the affected individuals. Affected individuals are mild to moderatementally retarded but they have no other associated abnormality. Blood sampleswere collected from five members including three affected (IV-1, IV-2, IV-6)and two normal individuals (III-2 and IV-7) and DNA was isolated using standardphenol-chloroform method.
FamilyBFamilyB is living in Mardan city of Khyber Pakhtunkhwa province. The pedigree wasconstructed after careful investigations with the family elders. This family has four generationscomprising of 11 members including two affected one male and one female (IV-2 and IV-3) figure.Consanguineous marriage has beenshown in the pedigree in 3rd generation and the disease appeared in 4thgeneration.Affected individuals are produced by normal parents which are carriers of thedisease, after lapse of generations, thus suggesting that the trait istransmitted in autosomal recessive mode.Clinical findings confirmed that thedisease was congenital autosomal recessive microcephaly and was not associatedto any environmental causes or part of syndrome.Bloodsamples were collected from five individuals of whom two were affected (IV-2 and IV-3) and three were nomal(III-1, III-2 and IV-1). Phenol-chloroform method wasfollowed for DNA extraction.
Genetic Mapping of Candidates Genesfor Autosomal Recessive Primary MicrocephalyOnthe basis of genetic linkage studies in autosomal recessive primary microcephaly,it is clear that at least some candidate intervals should be tested for linkageor exclusion prior to embarking on genome-wide scan. Seventeen candidate loci(MCPH 1-17) for autosomal recessive primary microcephaly are known. In the presentstudy, both the families were tested for linkage to these known loci bygenotyping microsatellite markers mapped within the candidate linkageintervals. Table 3.
1and 3.2 summarizesthe microsatellite markers in the region of known loci, which were used in thepresent study for candidate gene mapping.