Copper being an essential element to carry out different cellular processes normally is
maintained through proper regulation mechanisms to avoid its accumulation in the body. ATP7B
gene that codes for ATP dependent P type ATP7B protein controls the regulation of copper in
the body. It is required for the proper delivery of copper to apoceruloplasmin and its excretion
through bile in the form of feces. Therefore, mutation occurring in the ATP7B gene can cause
excessive cellular copper accumulation which results into Wilson’s disease. Variation in ATP7B
gene related to copper transportation leads to Wilson’s disease and transmitted in generation
through recessive pattern of inheritance.
For this study blood samples of fifteen Wilson’s disease affected patients along with
normal individuals of the same family were collected from Children's Hospital & Institute of
Child Health, Lahore. DNA was extracted from blood through organic extraction method
followed by DNA quantification. Amplification of exons 8, 13, 14 and 18 of ATP7B gene was
performed after designing specific primers for these specific regions. Sequencing of amplified
products was done through dideoxy chain termination method. A disease causing mutation of
ATP7B gene c.3155 C>T; p1052 Proline (CCC) to Leucine (CTC) has been mapped on exon 14
in family with Wilson’s disease. This mutation can be used for genetic testing, prenatal
diagnosis and genetic counseling. No mutation was found in exons 8, 13 and 18 which mean that
further study needs to be done to find more local mutation(s) that can be used for fast direct
genetic testing of Wilson’s disease patients or the carriers with heterozygotic conditions who can
develop this disease at any age of their life.
Results
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MUSCLE and Clustal Omega were used for homology analysis of ATP7B gene
nucleotide and protein sequences that revealed Gorilla to be closest to human regarding coding
sequences, while Clustal Omega output file showed all the species varied highly in their protein
structure homologies. Through the prediction of secondary structure homologies it was seen that
marmoset was closest to humans.
This study helped in providing prenatal diagnosis and genetic screening services in the
country. It has facilitated in selecting animal models for further study and research on ATP7B
gene and molecular pathogenesis of the Wilson’s disease leading to prevention and cure of
disease.