Nuclear mitochondrial interplay in the modulation of the homopolymeric tract length heteroplasmy in the control (D-loop) region of the mitochondrial DNA

We have studied the genetic characteristics of a homopolymeric tract length heteroplasmy associated with the 16189C variant in the mtDNA D-loop control region to identify the factor(s) involved in the generation of the length heteroplasmy. The relative proportion of the various lengths of the polycytosines (i.e., the pattern of the length heteroplasmy) is maintained in an individual, and previous evidence shows that it is regenerated de novo following cell divisions. The pattern is maintained in maternally related individuals, suggestive of mtDNA determinants. Of the 38 individuals with the 16189C variant studied, 39% were found to exhibit the (16180)AAACCCCCCCCCCC(16193) variant associated with A16183C polymorphism [(11C)-group], while 53% showed the (16180)AACCCCCCCCCCCC(16193) variant associated with a further A16182C polymorphism [(12C)-group]. Haplotype analysis of the mtDNA revealed a specific association of the longer mean length of the poly[C] in the (12C)-group with haplogroup B. A similar association was also observed in the (11C)-group, but with a novel haplogroup. Cybrid constructions revealed that the involvement of nuclear factor(s) in the generation of the length heteroplasmy is prominent in homopolymeric tract of eight cytosines. The nuclearly coded factor(s) is/are presumably related to the fidelity of the nuclearly coded components of the mitochondrial DNA replication machinery.     

Mitochondrial DNA and the Y chromosome suggest the settlement of Madagascar by Indonesian sea nomad populations

Background

Linguistic, cultural and genetic characteristics of the Malagasy suggest that both Africans and Island Southeast Asians were involved in the colonization of Madagascar. Populations from the Indonesian archipelago played an especially important role because linguistic evidence suggests that the Malagasy language branches from the Southeast Barito language family of southern Borneo, Indonesia, with the closest language spoken today by the Ma’anyan. To test for a genetic link between Malagasy and these linguistically related Indonesian populations, we studied the Ma’anyan and other Indonesian ethnic groups (including the sea nomad Bajo) that, from their historical and linguistic contexts, may be modern descendants of the populations that helped enact the settlement of Madagascar.

Result

A combination of phylogeographic analysis of genetic distances, haplotype comparisons and inference of parental populations by linear optimization, using both maternal and paternal DNA lineages, suggests that Malagasy derive from multiple regional sources in Indonesia, with a focus on eastern Borneo, southern Sulawesi and the Lesser Sunda islands.

Conclusion

Settlement may have been mediated by ancient sea nomad movements because the linguistically closest population, Ma’anyan, has only subtle genetic connections to Malagasy, whereas genetic links with other sea nomads are more strongly supported. Our data hint at a more complex scenario for the Indonesian settlement of Madagascar than has previously been recognized.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1394-7) contains supplementary material, which is available to authorized users.     

Hypnozoite depletion in successive Plasmodium vivax relapses

Genotyping Plasmodium vivax relapses can provide insights into hypnozoite biology. We performed targeted amplicon sequencing of 127 relapses occurring in Indonesian soldiers returning to malaria-free Java after yearlong deployment in malarious Eastern Indonesia. Hepatic carriage of multiple hypnozoite clones was evident in three-quarters of soldiers with two successive relapses, yet the majority of relapse episodes only displayed one clonal population. The number of clones detected in relapse episodes decreased over time and through successive relapses, especially in individuals who received hypnozoiticidal therapy. Interrogating the multiplicity of infection in this P. vivax relapse cohort reveals evidence of independent activation and slow depletion of hypnozoites over many months by multiple possible mechanisms, including parasite senescence and host immunity.     

Planar cell polarity induces local microtubule bundling for coordinated ciliary beating

Multiciliated cells (MCCs) in tracheas generate mucociliary clearance through coordinated ciliary beating. Apical microtubules (MTs) play a crucial role in this process by organizing the planar cell polarity (PCP)–dependent orientation of ciliary basal bodies (BBs), for which the underlying molecular basis remains elusive. Herein, we found that the deficiency of Daple, a dishevelled-associating protein, in tracheal MCCs impaired the planar polarized apical MTs without affecting the core PCP proteins, causing significant defects in the BB orientation at the cell level but not the tissue level. Using live-cell imaging and ultra-high voltage electron microscope tomography, we found that the apical MTs accumulated and were stabilized by side-by-side association with one side of the apical junctional complex, to which Daple was localized. In vitro binding and single-molecule imaging revealed that Daple directly bound to, bundled, and stabilized MTs through its dimerization. These features convey a PCP-related molecular basis for the polarization of apical MTs, which coordinate ciliary beating in tracheal MCCs.     

A Polynesian motif on the Y chromosome: population structure in remote Oceania

The Polynesian motif, a mitochondrial DNA marker of ancestral Polynesian communities, has filled a critical role in reconstructions of remote Oceanic history. Although the motif provides an effective narrative for Polynesian females, no equivalent male history is available from paternal lineages. Here, we describe a Y-chromosome binary polymorphism with absolute Polynesian affinity. We illustrate its unique spatial and temporal connections to early Polynesian communities, and through an analysis of associated short tandem repeat variation, we describe the first clear genealogic structure within Polynesia. Unlike the eastern and western regions advocated by archeology, we identify a tripartite structure comprising interaction spheres in the west (Tonga and Samoa), center (Tahiti), and east (Rapanui/Easter Island). Such patterning, a product of early regional contact and subsequent isolation, signals the conflicting roles of mobility and seclusion in Polynesian prehistory.     

Episodes of Diversification and Isolation in Island Southeast Asian and Near Oceanian Male Lineages

Island Southeast Asia (ISEA) and Oceania host one of the world’s richest assemblages of human phenotypic, linguistic, and cultural diversity. Despite this, the region’s male genetic lineages are globally among the last to remain unresolved. We compiled ∼9.7 Mb of Y chromosome (chrY) sequence from a diverse sample of over 380 men from this region, including 152 first reported here. The granularity of this data set allows us to fully resolve and date the regional chrY phylogeny. This new high-resolution tree confirms two main population bursts: multiple rapid diversifications following the region’s initial settlement ∼50 kya, and extensive expansions <6 kya. Notably, ∼40–25 kya the deep rooting local lineages of C-M130, M-P256, and S-B254 show almost no further branching events in ISEA, New Guinea, and Australia, matching a similar pause in diversification seen in maternal mitochondrial DNA lineages. The main local lineages start diversifying ∼25 kya, at the time of the last glacial maximum. This improved chrY topology highlights localized events with important historical implications, including pre-Holocene contact between Mainland and ISEA, potential interactions between Australia and the Papuan world, and a sustained period of diversification following the flooding of the ancient Sunda and Sahul continents as the insular landscape observed today formed. The high-resolution phylogeny of the chrY presented here thus enables a detailed exploration of past isolation, interaction, and change in one of the world’s least understood regions.     

A small cohort of Island Southeast Asian women founded Madagascar

The settlement of Madagascar is one of the most unusual, and least understood, episodes in human prehistory. Madagascar was one of the last landmasses to be reached by people, and despite the island's location just off the east coast of Africa, evidence from genetics, language and culture all attests that it was settled jointly by Africans, and more surprisingly, Indonesians. Nevertheless, extremely little is known about the settlement process itself. Here, we report broad geographical screening of Malagasy and Indonesian genetic variation, from which we infer a statistically robust coalescent model of the island's initial settlement. Maximum-likelihood estimates favour a scenario in which Madagascar was settled approximately 1200 years ago by a very small group of women (approx. 30), most of Indonesian descent (approx. 93%). This highly restricted founding population raises the possibility that Madagascar was settled not as a large-scale planned colonization event from Indonesia, but rather through a small, perhaps even unintended, transoceanic crossing.     

Patterns of Y-chromosome diversity intersect with the Trans-New Guinea hypothesis

The island of New Guinea received part of the first human expansion out of Africa (>40,000 years ago), but its human genetic history remains poorly understood. In this study, we examined Y-chromosome diversity in 162 samples from the Bird's Head region of northwest New Guinea (NWNG) and compared the results with previously obtained data from other parts of the island. NWNG harbors a high level of cultural and linguistic diversity and is inhabited by non-Austronesian (i.e., Papuan)-speaking groups as well as harboring most of West New Guinea's (WNG) Austronesian-speaking groups. However, 97.5% of its Y-chromosomes belong to 5 haplogroups that originated in Melanesia; hence, the Y-chromosome diversity of NWNG (and, according to available data, of New Guinea as a whole) essentially reflects a local history. The remaining 2.5% belong to 2 haplogroups (O-M119 and O-M122) of East Asian origin, which were brought to New Guinea by Austronesian-speaking migrants around 3,500 years ago. Thus, the Austronesian expansion had only a small impact on shaping Y-chromosome diversity in NWNG, although the linguistic impact of this expansion to this region was much higher. In contrast, the expansion of Trans-New Guinea (TNG) speakers (non-Austronesian) starting about 6,000-10,000 years ago from the central highlands of what is now Papua New Guinea, presumably in combination with the expansion of agriculture, played a more important role in determining the Y-chromosome diversity of New Guinea. In particular, we identified 2 haplogroups (M-P34 and K-M254) as suggestive markers for the TNG expansion, whereas 2 other haplogroups (C-M38 and K-M9) most likely reflect the earlier local Y-chromosome diversity. We propose that sex-biased differences in the social structure and cultural heritage of the people involved in the Austronesian and the TNG expansions played an important role (among other factors) in shaping the New Guinean Y-chromosome landscape.