Abstract
Xeroderma pigmentosum (XP) is a rare, genetic, autosomal nucleotide excision repair-deficient disease characterized by sun-sensitivity and early appearance of skin and ocular tumors. Thirty-two black-skinned XP from Comoros, located in the Indian Ocean, were counted, rendering this area the highest world prevalence of XP. These patients exhibited a new homozygous XPC mutation at the 3’-end of the intron12 (IVS 12-1G>C) leading to the absence of XPC protein. This mutation, characteristic of the consanguineous Comorian families, is associated with a founder effect with an estimated age of about 800 years. Analysis of mt-DNA and Y-chromosome identified the haplogroups of patients, who are derived from the Bantu people. Although the four Comorian islands were populated by the same individuals during the 7-10th centuries, XP was found now only in the Comorian island of Anjouan. To avoid the slavery process caused by the arrival of the Arabs around the 11-13th centuries, inhabitants of Anjouan, including XP-heterozygotes, hid inland of the island protected by volcanoes. This population lived with an endogamic style, without connection with the other islands. XP patients still live in the same isolated villages as their ancestries. Local history and geography may, thus, explain the high incidence of XP located exclusively in one island.
Highlights
Xeroderma pigmentosum (XP) is a rare genetic autosomal recessive disease caused by a defect in the Nucleotide Excision Repair (NER) pathway (Kraemer and Sarasin, 2018; Sarasin et al, 2019)
May be the frequency of XP heterozygote Africans who crossed the sea from East Africa to Comoros, was low enough that statistically no or a too small number of such individuals arrived in the other islands? we found only four different haplogroups in the Y chromosome and four different haplogroups in the mtDNA for the origins of the Comorian XP-C parents (Table 1), indicating that the number of ancestral XP heterozygotes was probably small during the Comoros peopling
The four islands were accessed by these individuals, but only the Anjouan Island could accumulate, protect and propagate XP-C families
Summary
Xeroderma pigmentosum (XP) is a rare genetic autosomal recessive disease caused by a defect in the Nucleotide Excision Repair (NER) pathway (Kraemer and Sarasin, 2018; Sarasin et al, 2019). About 50% of XP patients in the world are mutated in the XPC gene The cells of these particular patients are deficient in global genome repair, but proficient in transcription-coupled repair (Sarasin and Stary, 2007; Hanawalt and Spivak, 2008). These patients are very sensitive to sun exposure, at a very high risk of developing skin cancers (basal-and squamous-cell carcinomas, and melanomas), but they show normal development and growth, and no neurological abnormalities
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