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<p>The major histocompatibility complex (MHC) class II DRB1 locus is a key component of the vertebrate adaptive immune system, encoding the β-chain of the MHC class II molecule involved in presenting processed antigens to CD4<sup>+</sup> T cells. In the present investigation, the coding sequence, nucleotide architecture, codon usage characteristics, amino acid composition, and phylogenetic relationships of the MHC DRB1 gene were examined in the Indian dromedary camel (<i>Camelus dromedarius</i>). Five gene fragments encompassing all six exons of the DRB1 gene were amplified through polymerase chain reaction–sequence-based typing (PCR-SBT) and subsequently sequenced using Sanger chain-termination technology. Assembly and annotation of the obtained sequences revealed a complete coding region of 813&#xa0;bp, translating into a polypeptide comprising 270 amino acids. Nucleotide and protein composition, codon adaptation index (CAI), relative synonymous codon usage (RSCU), and effective number of codons (ENC) were evaluated using the CAIcal platform. Nucleotide composition analysis revealed a GC-rich coding sequence (58.92%), with the third codon position exhibiting the highest GC content. Computational analysis identified a CpG island spanning positions 108–447, indicating a possible role in transcriptional regulation. Codon usage assessment suggested an intermediate level of codon bias, reflected by an ENC value of 45.5 and a CAI value of 0.752. RSCU values varied considerably (0–4.25), with CTG identified as the most preferred codon. Analysis of the deduced amino acid sequence demonstrated that valine, glycine, and leucine were the predominant residues in the DRβ1 protein. Comparative sequence evaluation further revealed a camelid-specific insertion of 12 nucleotides within exon 2, giving rise to four additional amino acids (GEQG) in the β1 domain. Phylogenetic analysis using the neighbor-joining method demonstrated close clustering of Indian dromedary camel with other camelid species, confirming their evolutionary relationship. These findings provide a comprehensive molecular characterization of the camel MHC DRB1 gene and offers valuable insights into its sequence organization, codon usage preferences, and evolutionary history. The present study aligns with UN’s sustainable development goals, SDG-2 and 15, facilitating genetic strategies into camel immune-genetics for enhanced disease resistance and biodiversity conservation.</p>

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Molecular characterization and evolutionary analysis of the MHC Class II DRB1 gene in Indian dromedary camel (Camelus dromedarius)

  • 期刊论文

  • 发表日期：

    2026年7月22日

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  • Radha Rani Sawami,
  • Manju Nehara,
  • Basanti Jyotsana,
  • Urmila Pannu,
  • Suman,
  • Ved Prakash

摘要

The major histocompatibility complex (MHC) class II DRB1 locus is a key component of the vertebrate adaptive immune system, encoding the β-chain of the MHC class II molecule involved in presenting processed antigens to CD4+ T cells. In the present investigation, the coding sequence, nucleotide architecture, codon usage characteristics, amino acid composition, and phylogenetic relationships of the MHC DRB1 gene were examined in the Indian dromedary camel (Camelus dromedarius). Five gene fragments encompassing all six exons of the DRB1 gene were amplified through polymerase chain reaction–sequence-based typing (PCR-SBT) and subsequently sequenced using Sanger chain-termination technology. Assembly and annotation of the obtained sequences revealed a complete coding region of 813 bp, translating into a polypeptide comprising 270 amino acids. Nucleotide and protein composition, codon adaptation index (CAI), relative synonymous codon usage (RSCU), and effective number of codons (ENC) were evaluated using the CAIcal platform. Nucleotide composition analysis revealed a GC-rich coding sequence (58.92%), with the third codon position exhibiting the highest GC content. Computational analysis identified a CpG island spanning positions 108–447, indicating a possible role in transcriptional regulation. Codon usage assessment suggested an intermediate level of codon bias, reflected by an ENC value of 45.5 and a CAI value of 0.752. RSCU values varied considerably (0–4.25), with CTG identified as the most preferred codon. Analysis of the deduced amino acid sequence demonstrated that valine, glycine, and leucine were the predominant residues in the DRβ1 protein. Comparative sequence evaluation further revealed a camelid-specific insertion of 12 nucleotides within exon 2, giving rise to four additional amino acids (GEQG) in the β1 domain. Phylogenetic analysis using the neighbor-joining method demonstrated close clustering of Indian dromedary camel with other camelid species, confirming their evolutionary relationship. These findings provide a comprehensive molecular characterization of the camel MHC DRB1 gene and offers valuable insights into its sequence organization, codon usage preferences, and evolutionary history. The present study aligns with UN’s sustainable development goals, SDG-2 and 15, facilitating genetic strategies into camel immune-genetics for enhanced disease resistance and biodiversity conservation.