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ABO 遺伝子型はブタの GalNAc レベルを調節することで腸内細菌叢を変化させる

Sep 06, 2023Sep 06, 2023

Nature volume 606、pages 358–367 (2022)この記事を引用

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腸内微生物叢の構成は個人差が大きく、健康状態と相関しています1。 宿主の遺伝学がこの変異にどの程度、どのように寄与しているのかを理解することは不可欠であるが、特にヒトでは関連性が再現されていないため、困難であることが判明している2。 今回我々は、大規模なモザイク豚集団における腸内細菌叢の組成に対する宿主の遺伝子型の影響を研究します。 私たちは、遺伝的多様性と環境の均一性が悪化した条件下では、微生物叢の構成と特定の分類群の豊富さが遺伝性であることを示します。 私たちは、ツツジ科種の存在量に影響を与える量的形質遺伝子座をマッピングし、それがヒトの ABO 血液型を支える N-アセチル-ガラクトサミニル-トランスフェラーゼをコードする遺伝子の 2.3 kb の欠失によって引き起こされることを示します。 我々は、この欠失がバランス選択のもとでの350万年以上前の種間多型であることを示す。 我々は、それが腸内のN-アセチル-ガラクトサミンの濃度を減少させ、それによってN-アセチル-ガラクトサミンを輸入して異化することができる丹毒の存在量を減少させることを実証しました。 私たちの結果は、この関連性を支える分子機構についての洞察と併せて、腸内の特定の細菌の存在量に対する宿主の遺伝子型の影響についての非常に強力な証拠を提供します。 私たちのデータは、農村部の人間集団における同様の影響を特定するための道を開きます。

生物の生理機能と病理学を包括的に理解するには、宿主とその複数の微生物叢の統合的な分析が必要であることがますます認識されています1。 ヒトでは、腸内微生物叢の組成は、HDL コレステロール、空腹時血糖値、BMI などの生理学的および病理学的パラメーターと関連しています2。 家畜では、第一胃マイクロバイオームの構成がメタン生成と飼料効率に関連しています3。 これらの相関関係は、宿主の生理機能に対するマイクロバイオームの直接的(因果的)影響を含む可能性のある、宿主と微生物叢の間の複雑な相互作用を反映しています4。 微生物叢の構成と相関するいくつかの表現型は遺伝性です5,6。 これは、宿主の遺伝子型が微生物叢の構成を部分的に決定し、それが宿主の表現型に影響を与える可能性があるという仮説につながります4。 これは、微生物叢の構成が部分的に遺伝することを意味します。 げっ歯類での研究はこれを裏付けていますが 7、人間では証拠はそれほど説得力がありません。 最初の報告では、二卵性双生児と比較して一卵性双生児間の微生物叢の類似性が高いことは明らかにされておらず、宿主の遺伝子型の影響が限定的であることが示唆されています8。 より精度の高い研究により、分類群、特にクリステンセネラ科の豊富さに対する宿主遺伝学の重大な影響の証拠が提供されました9。 微生物叢の遺伝性を支える遺伝子座をヒトで特定することは依然として困難である。 ラクターゼ (LCT) の持続的発現を引き起こし、ビフィズス菌存在量の減少に関連する変異体とは別に、他の GWAS 遺伝子座は複製が難しいことが証明されています 2,10,11,12,13,14。 微生物叢構成の遺伝的構造をより深く理解するには、より大規模なヒトコホートの分析が必要です。

大型の単胃雑食動物における腸内微生物叢組成の遺伝的構造を解読するために、我々はモザイクブタ集団の生成とその腸内微生物叢の縦断的特徴付けを報告する。 我々は、微生物叢の組成に対する宿主の遺伝子型の強い影響を観察し、腸内のN-アセチル-ガラクトサミンの濃度を制御することで、特定の分類群の存在量に大きな影響を与える遺伝子座を特定し、それによってこの代謝物を利用するいくつかの種に影響を与えました。炭素源。

7,500) mosaic population by intercrossing the offspring of 61 F0 founders from four Chinese and four western breeds for more than 10 generations (Supplementary Table 1 and Extended Data Fig. 1). Animals were reared in uniform housing and feeding conditions. We analysed more than 200 phenotypes (pertaining to body composition, physiology, disease resistance and behaviour), obtained transcriptome, epigenome and chromatin interaction data from multiple tissues, and collected plasma metabolome and microbiome data in up to 954 F6 and 892 F7 animals. The F0 animals were whole-genome sequenced at an average depth of 28.4-fold, and the F6 and F7 animals were sequence at an average depth of 8.0-fold. We called genotypes at 23.8 million single-nucleotide polymorphisms (SNPs) and 6.4 million insertion–deletions (indels) with a minor allele frequency (MAF) of ≥0.03 (>1/100 bp). The nucleotide diversity (π) (that is, the proportion of nucleotide sites that differ between homologous sequences in two breeds) between two Chinese breeds and between two European breeds was similar to that between Homo sapiens and Homo neanderthalensis (~3 × 10−3)15, whereas the π between a Chinese and a European breed approached half of that between human and chimpanzee (~4.3 × 10−3)16. The proportion of the eight founder genomes in F6 and F7 ranged from 11.2% to 14.7% at the genome level, and from 4.9% to 22.1% at the chromosome level. The median number of variants in high linkage disequilibrium (LD) (r2 ≥ 0.9) with an index variant was 30, and the median maximal distance with a variant in high LD (r2 ≥ 0.9) was 54 kb (Extended Data Fig. 1)./p>5% were filtered out. Non-redundant MAGs were generated by dRep (v.2.3.2) at threshold of 99% average nucleotide identity (ANI)92./p>

2-fold higher in domestic pigs than in human populations, as previously reported111,112,113. Nucleotide diversities between Chinese founder breeds and between European founder breeds were ~3.6x10−3 and ~2.5x10−3, respectively, i.e. 1.44-fold and 1.25-fold higher than the respective within-breed π-values. These π-values are of the same order of magnitude as the sequence divergence between Homo sapiens and Neanderthals/Denosivans (~3x10−3, ref. 15). By comparison, π-values between Africans, Asians and Europeans are typically ≤ ~1x10−3 (ref. 109). The nucleotide diversity between Chinese and European breeds averaged ~4.3x10−3. This π-value is similar to the divergence between M. domesticus and M. castaneus114, and close to halve the ~1% difference between chimpanzee and human16. Note that Chinese and European pig breeds are derived from Chinese and European wild boars, respectively, which are thought to have diverged ~1 million years ago27, while M. domesticus and M. castaneus are thought to have diverged ≤ 500,000 years ago114. (d) Autosome-specific estimates of the genomic contributions of the eight founder breeds in the F6 and F7 generation. We used a linear model incorporating all variants to estimate the average contribution of the eight founder breeds in the F6 and F7 generation at genome and chromosome level56. At genome-wide level, the proportion of the eight founder breed genomes ranged from 11.2% (respectively 11.5%) to 14.1% (14.7%) in the F6 (F7) generations. At chromosome-specific level, the proportion of the eight founder breeds ranged from 6.7% (respectively 4.9%) to 20.7% (22.1%) in the F6 (F7) generations. The genomic contribution of the eight founder breeds in the F6 and F7 generation is remarkably uniform and close to expectations (i.e. 12.5%) both at genome-wide and chromosome-wide level, suggesting comparable levels of genetic diversity across the entire genome. This does not preclude that more granular examination may reveal local departures from expectations, or under-representation of incompatible allelic combinations at non-syntenic loci. (e-f) Indicators of achievable mapping resolution in the F6 generation: (e) Frequency distribution (density) of the number of variants in high LD (r2 ≥ 0.9) with an “index” variant (was computed separately for all variants considered sequentially as the “index”), corresponding to the expected size of “credible sets” in GWAS115. The red vertical line corresponds to the genome-wide median. The green vertical line corresponds to the mapping resolution achieved in this study for the ABO locus (see hereafter). (f) Frequency distribution (density) of the maximum distance between an index variant and a variant in high LD (r2 ≥ 0.9) with it, defining the spread of credible sets. Red and green vertical lines are as in (D)./p>95% of day 120 and 240 faeces and caecum content samples of both F6 and F7 generations, hence defined as core bacterial taxa. (b) The compositions of the porcine and human intestinal microbiota are closer to each other than either is to that of the mouse. Boxplots are as is Fig. 1c. The number of samples available for analysis were 1281 pigs, 106 humans and 6 mice. (c) Abundances (F6-F7 averages when available) of the 43 families represented in Fig. 1b in the seven sample types relative to the sample type in which they are the most abundant (red – blue scale). The families are ordered according to the sample type in which they are the most abundant. The colour-code for phyla is as in Fig. 1b. Columns are added for comparison with mouse and human. Mouse data are from Fig. 1 in Suzuki & Nachman116, and human data from Fig. 6 in Vuik et al117. P_I: proximal ileum, D_IL: distal ileum, C: caecum, CO: colon, RE: rectum, F: faeces. The families differing the most with regards to location-specific distribution between species include Helicobacteriaceae, Veillonellaceae, Lactobacillaceae and Streptocaccaceae./p> 10 MYA. It will be interesting to study larger numbers of warthog to see whether the same 2.3 kb deletion exists in this and other related species as well. (b) Alignment of ~900 base pairs of the O alleles of domestic pigs (Bamaxian), European and Asian wild boars, and Sus cebufrons demonstrating that these are identical-by-descent. The SINE element that is presumed to have mediated the recombinational event that caused to 2.3 kb deletion is highlighted in red. Context: To further support their identity-by-descent we aligned ~900 base pairs (centred on the position of the 2.3 kb deletion) of the O alleles of domestic pig, European and Asian wild boars and Sus cebifrons. The sequences were nearly identical further supporting our hypothesis. It is noteworthy that the old age of the “O” allele must have contributed to the remarkable mapping resolution (≤3 kb) that was achieved in this study. In total, 42 variants were in near perfect LD (r2 ≥ 0.9) with the 2.3 kb deletion in the F0 generation, spanning 2,298 bp (1,522 on the proximal side, and 762 on the distal side of the 2.3 kb deletion). This 2.3 kb span is lower than genome-wide expectations (17th percentile), presumably due to the numerous cross-overs that have accrued since the birth of the 2.3 kb deletion that occurred in the distant past. Yet the number of informative variants within this small segment is higher than genome-wide average of (57% percentile) also probably due at least in part to the accumulation of numerous mutations since the remote time of coalescence of the A and O alleles (see Fig. 1d in main text). (c) QQ plots for the effect of AO genotype on 150 phenotypes pertaining to meat quality, growth, carcass composition, hematology, health, and other phenotypes in the F6 and F7 generation. P-values were obtained using a mixed model followed by meta-analysis (weighted Z score) across the F6 and F7 generations as described in Methods. log-transformed p-values used for the QQ plot are nominal and two-sided. Context: Our findings in suidae are reminiscent of the trans-species polymorphism of the ABO gene in primates attributed to balancing selection26. The phenotype driving balancing selection remain largely unknown yet a tug of war with pathogens is usually invoked: synthesized glycans may affect pathogen adhesion, toxin binding or act as soluble decoys, while naturally occurring antibodies may be protective20,44. In humans, the O allele may protect against malaria118, E. Coli and Salmonella enteric infection119, SARS-CoV-142, SARS-CoV-243 and schistosomiasis120,121,122, while being a possible risk factor for cholera123, H. pylori124 and norovirus infection125. Whatever the underlying selective force, it appears to have operated independently in at least two mammalian branches (primates and suidae), over exceedingly long periods of time, and over broad geographic ranges, hence pointing towards its pervasive nature. To gain insights in what selective forces might underpin the observed balanced polymorphism, we tested the effect of porcine AO genotype on >150 traits measured in the F6 and F7 generations pertaining to carcass composition, growth, meat quality, hematological parameters, disease resistance and behaviour. No significant effects were observed when accounting for multiple testing, including those pertaining to immunity and disease resistance. (d) Expression profile of the AO gene in a panel of adult and embryonic porcine tissues (own RNA-Seq data)./p>