Distinct positions of genetic and oral histories: Perspectives from India.

Over the past decade, genomic data have contributed to several insights on global human population histories. These studies have been met both with interest and critically, particularly by populations with oral histories that are records of their past and often reference their origins. While several studies have reported concordance between oral and genetic histories, there is potential for tension that may stem from genetic histories being prioritized or used to confirm community-based knowledge and ethnography, especially if they differ. To investigate the interplay between oral and genetic histories, we focused on the southwestern region of India and analyzed whole-genome sequence data from 156 individuals identifying as Bunt, Kodava, Nair, and Kapla. We supplemented limited anthropological records on these populations with oral history accounts from community members and historical literature, focusing on references to non-local origins such as the ancient Scythians in the case of Bunt, Kodava, and Nair, members of Alexander the Great's army for the Kodava, and an African-related source for Kapla. We found these populations to be genetically most similar to other Indian populations, with the Kapla more similar to South Indian tribal populations that maximize a genetic ancestry related to Ancient Ancestral South Indians. We did not find evidence of additional genetic sources in the study populations than those known to have contributed to many other present-day South Asian populations. Our results demonstrate that oral and genetic histories may not always provide consistent accounts of population origins and motivate further community-engaged, multi-disciplinary investigations of non-local origin stories in these communities.

The genetic admixture and assimilation of Ahom: a historic migrant from Thailand to India.

The Northeastern region of India is considered a gateway for modern humans' dispersal throughout Asia. This region is a mixture of various ethnic and indigenous populations amalgamating multiple ancestries. One reason for such amalgamation is that, South Asia experienced multiple historic migrations from various parts of the world. A few examples explored genetically are Jews, Parsis and Siddis. Ahom is a dynasty that historically migrated to India during the 12th century. However, this putative migration has not been studied genetically at high resolution. Therefore, to validate this historical evidence, we genotyped autosomal data of the Modern Ahom population residing in seven sister states of India. Principal Component and Admixture analyses haave suggested a substantial admixture of the Ahom population with the local Tibeto-Burman populations. Moreover, the haplotype-based analysis has linked these Ahom individuals mainly with the Kusunda (a language isolated from Nepal) and Khasi (an Austroasiatic population of Meghalaya). Such unexpected presence of widespread population affinities suggests that Ahom mixed and assimilated a wide variety of Trans-Himalayan populations inhabiting this region after the migration. In summary, we observed a significant deviation of Ahom from their ancestral homeland (Thailand) and extensive admixture and assimilation with the local South Asian populations.

Genetic evidence for a single founding population of the Lakshadweep Islands.

Lakshadweep is an archipelago of 36 islands located in the Southeastern Arabian Sea. In the absence of a detailed archaeological record, the human settlement timing of this island is vague. Previous genetic studies on haploid DNA makers suggested sex-biased ancestry linked to North and South Indian populations. Maternal ancestry suggested a closer link with the Southern Indian, while paternal ancestry advocated the Northern Indian genetic affinity. Since the haploid markers are more sensitive to genetic drift, which is evident for the Island populations, we have used the biparental high-resolution single-nucleotide polymorphic markers to reconstruct the population history of Lakshadweep Islands.  Using the fine-scaled analyses, we specifically focused on (A) the ancestry components of Lakshadweep Islands populations; (B) their relation with East, West Eurasia and South Asia; (C) the number of founding lineages and (D) the putative migration from Northern India as the paternal ancestry was closer to the North Indian populations. Our analysis of ancestry components confirmed relatively higher North Indian ancestry among the Lakshadweep population. These populations are closely related to the South Asian populations. We identified mainly a single founding population for these Islands, geographically divided into two sub-clusters. By examining the population's genetic composition and analysing the gene flow from different source populations, this study contributes to our understanding of Lakshadweep Island's evolutionary history and population dynamics. These findings shed light on the complex interactions between ethnic groups and their genetic contributions in making the Lakshadweep population.

Reconstructing the population history of the Sinhalese, the major ethnic group in Sri Lanka.

The Sinhalese are the major ethnic group in Sri Lanka, inhabiting nearly the whole length and breadth of the island. They speak an Indo-European language of the Indo-Iranian branch, which is held to originate in northwestern India, going back to at least the fifth century BC. Previous genetic studies on low-resolution markers failed to infer the genomic history of the Sinhalese population. Therefore, we have performed a high-resolution fine-grained genetic study of the Sinhalese population and, in the broader context, we attempted to reconstruct the genetic history of Sri Lanka. Our allele-frequency-based analysis showed a tight cluster of Sinhalese and Tamil populations, suggesting strong gene flow beyond the boundary of ethnicity and language. Interestingly, the haplotype-based analysis preserved a trace of the North Indian affiliation to the Sinhalese population. Overall, in the South Asian context, Sri Lankan ethnic groups are genetically more homogeneous than others.

Advancements and Challenges in Ancient DNA Research: Bridging the Global North-South Divide.

Ancient DNA (aDNA) research first began in 1984 and ever since has greatly expanded our understanding of evolution and migration. Today, aDNA analysis is used to solve various puzzles about the origin of mankind, migration patterns, and the spread of infectious diseases. The incredible findings ranging from identifying the new branches within the human family to studying the genomes of extinct flora and fauna have caught the world by surprise in recent times. However, a closer look at these published results points out a clear Global North and Global South divide. Therefore, through this research, we aim to emphasize encouraging better collaborative opportunities and technology transfer to support researchers in the Global South. Further, the present research also focuses on expanding the scope of the ongoing conversation in the field of aDNA by reporting relevant literature published around the world and discussing the advancements and challenges in the field.

The peopling of Lakshadweep Archipelago.

The archipelago of Lakshadweep is considered as a stopover to the maritime route since ancient time. It is not very clear when the human first occupied these islands, however in the long history of the islands, the local legends suggest that Lakshadweep has been ruled by different kingdoms. To have a better understanding of peopling of Lakshadweep, we have analysed 557 individuals from eight major islands for mitochondrial DNA and 166 individuals for Y chromosome markers. We found a strong founder effect for both paternal and maternal lineages. Moreover, we report a close genetic link of Lakshadweep islanders with the Maldives, Sri Lanka and India. Most of the Lakshadweep islands share the haplogroups specific to South Asia and West Eurasia, except Minicoy Island that also shares haplogroups of East Eurasia. The paternal and maternal ancestries of the majority of island populations suggest their arrival from distinct sources. We found that the maternal ancestry was closer to South Indian populations, whereas the paternal ancestry was overwhelmed with the haplogroups, more common in the Maldives and North of India. In conclusion, our first genetic data suggest that the majority of human ancestry in Lakshadweep is largely derived from South Asia with minor influences from East and West Eurasia.

Screening of mitochondrial mutations and insertion-deletion polymorphism in gestational diabetes mellitus in the Asian Indian population.

In this study we scrutinized the association between the A8344G/A3243G mutations and a 9-bp deletion polymorphism with gestational diabetes mellitus (GDM) in an Asian Indian population. The A3243G mutation in the mitochondrial tRNA(Leu(UUR)) causes mitochondrial encephalopathy myopathy, lactic acidosis, and stroke-like episodes (MELAS), while the A8344G mutation in tRNA(Lys) causes myoclonus epilepsy with ragged red fibers (MERRF). We screened 140 pregnant women diagnosed with GDM and 140 non-GDM participants for these mutations by PCR-RFLP analysis. Both A3243G and A8344G were associated with GDM (A3243: OR-3.667, 95% CI = 1.001-13.43, p = 0.03; A8344G: OR-11.00, 95% CI = 0.6026-200.8, p = 0.04). Mitochondrial DNA mutations contribute to the development of GDM. Our results conclude that mitochondrial mutations are associated with the GDM women in our population. Thus it is important to screen other mitochondrial mutations in the GDM women.

Altered transcription and expression of PTEN in breast tumors: is it regulated by hypermethylation?

Breast cancer (BC) is the commonest cancer in women worldwide with a widely variable incidence between countries and regions. BC is either familial or sporadic. Mutations in tumor suppressor gene, PTEN has been associated with syndromic BC and in a subset of sporadic BCs. The present study was carried out in archival formalin fixed paraffin embedded samples. Immunohistochemistry and quantitative RTPCR indicated a reduced expression/ transcription of PTEN in tumor as compared to adjacent non-tumorous tissue. However, the promoter methylation evaluated by Methylation Specific Restriction Assay indicated that only 20% of the tumors showed PTEN methylation and could not account for the rest of the samples with reduced expression. Overall evidence from literature and our present findings indicate that: (i) Loss of Heterozygosity at PTEN gene locus (ii) germline and somatic gene mutations of PTEN (iii) epigenetic silencing by methylation in PTEN promoter CpG cluster (iv)protein interactions which reduce PTEN transcription and (v) PTEN protein degradation together play an important role in the etiology of BC.

Evaluation of Aurora-A gene polymorphism and esophageal cancer risk in a South Indian population.

AIM: Aurora-A is a serine/threonine protein kinase that functions in centrosome maturation and spindle assembly and is involved in regulating chromosome segregation. It is amplified and overexpressed in several human cancers. The aim of the present study was to assess the role of T91A Aurora-A gene polymorphism associated with aneuploidy in human tumors. RESULT: Patients with different upper gastrointestinal tract symptoms who were referred for endoscopy were studied. They were categorized as individuals with esophageal cancer, esophagitis, and normal endoscopy based on endoscopy and histology reports. Healthy volunteers were used as controls for carrying out genomic polymerase chain reaction followed by restriction digestion. The cancer and esophagitis groups showed a higher percentage of cases with the TA genotype compared with the controls and gastrointestinal tract normal endoscopy samples. However, only esophagitis, despite a small sample size, showed a statistically significant association with the TA genotype (odds ratio=3.6082, 95% class interval=1.1276-8.8346, p=0.0411). It was also assessed if the T91A polymorphism plays a role in enhancing the effects of exogenous factors such as smoking, alcohol, tea, betel chewing, and nonvegetarian diet in esophageal pathologies. CONCLUSION: Our results indicate that the TT genotype is protective against these factors as a higher percentage of this genotype was found in individuals with normal endoscopy. This is the first study, to the best of our knowledge, carried out in an Indian population to evaluate the association of Aurora-A gene polymorphism with esophageal cancer.

Regulation of IGF2 transcript and protein expression by altered methylation in breast cancer.

PURPOSE: Breast Cancer is one of the leading causes of cancer deaths among women worldwide. The role of epigenetics as a distinct mechanism to alter gene expression in a tissue-specific manner has emerged as an important mechanism in the pathophysiology of cancer. Present study was carried out to assess the role of methylation in regulating transcription and protein expression of Insulin-like growth factor 2 (IGF2), an oncogene with parental imprinting. METHODS: Paraffin-embedded archival breast tumor and adjacent normal tissue samples were used for carrying out PCR-based methylation assay, genomic PCR, immunohistochemistry and Real-Time Reverse transcriptase PCR. RESULTS: A significant loss of methylation in exon 9 CpG cluster of IGF2 in breast tumor tissues was observed when compared to normal tissue (P < 0.0001). Expression of IGF2 by immunohistochemistry exhibited a mean twofold increase correlating with the hypomethylation of this specific CpG. Real-Time RT PCR showed increased transcripts in the tumor tissue supporting the IHC and methylation results. A total of 33% of tumor samples heterozygous for the ApaI IGF2 polymorphism exhibited biallelic IGF2 expression due to loss of imprinting; this was not seen in any of the normal breast tissues. CONCLUSIONS: Altered methylation of exonic CpG plays an important role in the enhanced transcription/expression of IGF2 in breast tumors. Methylation analysis of exon 9 CpG can be used as a biomarker for upregulation of IGF2 in breast tumor tissue and maybe developed as a diagnostic test in future.