RESUMO
Camelids are characterized by their unique adaptive immune system that exhibits the generation of homodimeric heavy-chain immunoglobulins, somatic hypermutation of T-cell receptors, and low genetic diversity of major histocompatibility complex (MHC) genes. However, short-read assemblies are typically highly fragmented in these gene loci owing to their repetitive and polymorphic nature. Here, we constructed a chromosome-level assembly of wild Bactrian camel genome based on high-coverage long-read sequencing and chromatin interaction mapping. The assembly with a contig N50 of 5.37 Mb and a scaffold N50 of 76.03 Mb, represents the most contiguous camelid genome to date. The genomic organization of immunoglobulin heavy-chain locus was similar between the wild Bactrian camel and alpaca, and genes encoding for conventional and heavy-chain antibodies were intermixed. The organizations of two immunoglobulin light-chain loci and four T cell receptor loci were also fully deciphered using the new assembly. Additionally, the complete classical MHC region was resolved into a single contig. The high-quality assembly presented here provides an essential reference for future investigations examining the camelid immune system.
Assuntos
Camelus/genética , Camelus/imunologia , Cromossomos/genética , Cromossomos/imunologia , Sistema Imunitário/imunologia , Animais , Genoma/genética , Genoma/imunologia , Genômica/métodos , Cadeias Pesadas de Imunoglobulinas/genética , Cadeias Pesadas de Imunoglobulinas/imunologia , Cadeias Leves de Imunoglobulina/genética , Cadeias Leves de Imunoglobulina/imunologia , MasculinoRESUMO
The domestic Bactrian camels were treated as one of the principal means of locomotion between the eastern and western cultures in history. However, whether they originated from East Asia or Central Asia remains elusive. To address this question, we perform whole-genome sequencing of 128 camels across Asia. The extant wild and domestic Bactrian camels show remarkable genetic divergence, as they were split from dromedaries. The wild Bactrian camels also contribute little to the ancestry of domestic ones, although they share close habitat in East Asia. Interestingly, among the domestic Bactrian camels, those from Iran exhibit the largest genetic distance and the earliest split from all others in the phylogeny, despite evident admixture between domestic Bactrian camels and dromedaries living in Central Asia. Taken together, our study support the Central Asian origin of domestic Bactrian camels, which were then immigrated eastward to Mongolia where native wild Bactrian camels inhabit.
