Genetic Study of Lct- Enhancer, Y Chromosome and Mitochondrial Dna Variation in Some Ethnic Groups in Ethiopia

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Addis Ababa University


Genetic Study of LCT- Enhancer, Y chromosome and Mitochondrial DNA Variation in Some Ethnic Groups in Ethiopia Solomon Balami Adugna (PhD Candidate) Addis Ababa University, 2018 Ethiopia has been the centre of Human out of African migration and thus occupies a strategic place to study of human evolutionary population genetics. It is regarded as a centre where key evolutionary events have taken place; as a place of human origin, a corridor for human migration and centre for origin of earlier human culture. Despite of the importance of Ethiopian population genetics, the human population genetic studies across geographically, ethnically and linguistically diverse Ethiopia population is still not exhaustively covered and understood. To contribute to these, genomic DNA was collected from five ethnic groups of Ethiopia; Nuer, Berta, Gumuz, Shinasha and Mao to examine the correlation of LP phenotype with genotype and study the patterns of Y chromosome and Mitochondrial DNA Variations. From these groups, a total of 155 participants, representing two language families; Afro-Asiatic and Nilo-Saharan in Ethiopia, were recruited for genetic analysis. The phenotypes of the lactase persistence (LP) were examined using breathe hydrogen test (BHT). The result showed that 83 (53.55%) and 68 (43.87%) of the total 155 study subject had a positive breath (≥20 ppm) and negative breath test (<20 ppm) respectively. Individuals with positive breath test are LP, while those with negative breath test are lactase non persistence (LNP). Moreover, 4 (2.58%) of NHP individuals were also observed. Milk drinking behavior and post gastrointestinal symptoms was also recorded. The higher frequency of LP was observed in the milk drinkers on the daily basis than the non milk drinkers. In all groups, majority of the LNP and very few LP individuals showed various post gastrointestinal symptoms. Y chromosomes and mitochondrial variation were studied in Ethiopian populations. The Y chromosome haplogroup variations were studied by typing four major Y haplogroups (A, B E and F) in 120 unrelated adult males. The Y chromosome study showed that the Ethiopian populations studied contain haplogroup A-M13, B-M60, E-M78 and F-M89 in percentages of 44.04, 39.28, 86.11 and 21.42 % respectively, showing higher Y chromosome diversity in Ethiopia than elsewhere in Africa. The ancient and deepest haplogroups A-M13 and B-M60 and the most widespread haplogroup E-M78 was present at such high frequencies in Nilo-Saharan than Afro-Asiatic speaking groups. Intersetingly, haplogroup E-M78 which is defined by E1b1b1a1 terminal branch was found at remarkably high frequency in present study. Based on sequencing of the mitochondrial Cytochrome C Oxidase subunit II (MT-COXII), 15 substitutions as SNPs were observed, of which the majority (80%) were Transitions. Of 15, 5 SNPs were new mutations. From mitochondrial haplotype variations analysis, a total of 13 haplotypes with 138 polymorphic sites were observed. Also, the evidence for the sign of past demographic expansion and higher genetic diversity was noted. Moreover, phylogenetic analyses indicate that East Africans in general and Western Ethiopia in particular contains more ancestral lineages in comparison to various continental populations placing them at the root of the human evolutionary tree. The results also confirm East Africa as the most probable location from which dissemination of human out of Africa has taken place. The study shows the higher level of MT-COXII sequence variation within Ethiopia in comparison to other East Africans and the continental samples, and suggests further detailed studies on Ethiopian population to contribute in filling the existing gaps in the MT-COXII database. This data implicated in the need to carry out detailed studies of human genetic variation that includes more African populations; particularly Ethiopians.



LP/LNP, BHT, Y Chromosome, MT-COXII, Haplogroup, PCR-RFLP