{
  "id": 18301014,
  "title": "Genomic architecture of the major histocompatibility complex genes in the Neotropical Midas cichlid",
  "url": "https://urgent.news/2026/11/05/genomic-architecture-of-the-major-histocompatibility-complex-genes-in",
  "topic": "science",
  "section": "Science",
  "published": "2026-11-05T00:00:00.000Z",
  "source": {
    "name": "bioRxiv",
    "slug": "biorxiv",
    "url": "https://www.biorxiv.org/content/10.64898/2026.11.04.764204v1?rss=1"
  },
  "original_language": "en",
  "account": "The Major Histocompatibility Complex (MHC) is crucial for adaptive immunity in vertebrates, but its genomic structure remains underexplored in many model organisms, such as the Neotropical Midas cichlid Amphilophus citrinellus. This study presents a thorough analysis of the MHC repertoire in this cichlid, utilizing various genomic techniques.\n\nThe researchers identified 298 MHC-related genetic loci spread across 18 chromosomes. Among these, 30 were MHC-I genes, 15 were MHC-IIA genes, and 20 were MHC-IIB genes, along with genes involved in antigen processing and regulation. Importantly, MHC-I and MHC-II genes were found on different chromosomes, which aligns with the non-linkage pattern observed in many teleost fish species.\n\nThe study also revealed that gene duplication and phylogenetic patterns indicate a birth-and-death evolution, contributing to a structurally diverse MHC repertoire with widely conserved protein domains. However, the distribution of transposable elements varied across MHC regions, which might have played a role in genomic diversification.\n\nFurther molecular analyses showed positive selection in MHC-I and IIB genes, whereas MHC-IIA exhibited more limited evidence of positive selection. Expression of MHC genes varied across tissues, with notable high expression in the spleen and thymus. Structural modeling confirmed that these genes retained their characteristic MHC folds.\n\nFinally, phylogenetic analysis positioned the MHC sequences of the Midas cichlid within a broader multilocus repertoire. This finding suggests that population-level diversity in the MHC may arise from a combination of allelic polymorphism and variation among paralogous loci. Overall, this comprehensive, chromosome-resolved characterization of the MHC in the Neotropical Midas cichlid offers a valuable genomic framework for future investigations into immune gene diversification during the cichlid radiation.",
  "summary": "The Major Histocompatibility Complex (MHC) plays a central role in vertebrate adaptive immunity, yet its genomic architecture remains poorly characterized in many evolutionary model systems, including the Neotropical Midas cichlid Amphilophus citrinellus. Here, we integrate chromosome-level functional genome annotation, transposable element (TE) profiling, transcriptomics, phylogenetics,…",
  "key_points": [],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}