Maintaining functional major histocompatibility complex diversity under inbreeding: the case of a selfing vertebrate

Major histocompatibility complex (MHC) genes encode proteins that present pathogen-derived antigens to T-cells, initiating the adaptive immune response in vertebrates. Although populations with low MHC diversity tend to be more susceptible to pathogens, some bottlenecked populations persist and even increase in numbers despite low MHC diversity. Thus, the relative importance of MHC diversity versus genome-wide variability for the long-term viability of populations after bottlenecks and/or under high inbreeding is controversial. We tested the hypothesis that genome-wide inbreeding (estimated using microsatellites) should be more critical than MHC diversity alone in determining pathogen resistance in the self-fertilising fish Kryptolebias marmoratus by analysing MHC diversity and parasite loads in natural and laboratory populations with different degrees of inbreeding. Both MHC and neutral diversities were lost after several generations of selfing, but we also found evidence of parasite s...主要组织相容性复合体（Major histocompatibility complex, MHC）基因编码的蛋白质可将病原体来源的抗原呈递至T细胞，从而启动脊椎动物的适应性免疫应答。尽管MHC多样性较低的种群往往更易受病原体感染，但部分经历过种群瓶颈的种群即便MHC多样性较低，仍能存续甚至种群数量得以增长。因此，在种群瓶颈事件后及/或高近交状态下，相较于全基因组变异，MHC多样性对于种群长期存续的相对重要性仍存在争议。本研究以自交繁殖鱼类斑纹隐小鳉（Kryptolebias marmoratus）为研究对象，通过分析不同近交程度的自然种群与实验种群的MHC多样性及寄生虫负荷，验证了"基于微卫星（microsatellites）估算的全基因组近交水平，相较于单纯的MHC多样性，对种群病原体抗性的影响更为关键"这一假说。经多代自交后，种群的MHC多样性与中性遗传多样性均出现丢失；同时本研究还发现了寄生虫相关的……