ヒトゲノム多様性研究室

自然選択がゲノムに与える影響


生物の遺伝子やゲノムには、正や負の自然選択が作用しています。集団遺伝学・分子進化学に基づく数理統計手法を用いて、自然選択が作用してきた遺伝子やゲノム領域を検出することができます。
正の自然選択

分子進化の大部分は中立的な変異の蓄積に起因しますが、生物進化の過程で表現型に大きな影響を及ぼした変異の中には正の自然選択が作用したものが多いと考えられます。私たちは、遺伝子配列解析・多型解析・統計解析・コンピュータシミュレーションによって、正の自然選択が作用して進化してきた遺伝子を同定し、その分子進化のメカニズムを解明したいと考えています。特に着目しているのは、有利なアリルが未だ固定には至っていない最近の正の自然選択についてです。連鎖不平衡の程度から、最近の正の自然選択のターゲットとなった変異の選択強度や誕生時期を推定することができます。また、関連解析などによって、自然選択の対象となった表現型を知ることも可能です。
Coriell社より購入したHapMapサンプルを用いて、HapMapプロジェクトでは調べられていない(データベースに登録されていない)多型の解析を行い、周辺多型との連鎖不平衡の程度から、最近の正の自然選択が作用してきたアリルを同定する試みも行っています。


その他の研究はこちら    

  本研究に関する文献


Nakayama K,Ohashi J, Watanabe K, Munkhtulga L, Iwamoto S. Evidence for very recent positive selection in Mongolians. Molecular Biologyand Evolution (in press)


Yasukochi Y, Ohashi J (2017) Elucidating the origin of HLA-B*73 allelic lineage: Did modern humans benefit by archaicintrogression? Immunogenetics 69: 63-67.


Yasukochi Y, Naka I, Patarapotikul J, Hananantachai H, Ohashi J (2017) Evolution of Fseg/Cseg dimorphism in region III ofPlasmodium falciparum eba-175 gene. Infection, Genetics and Evolution 49: 251?255.


Ohashi J, Suzuki Y, Naka I, Hananantachai H, Patarapotikul J (2014) Diversifying selection on the thrombospondin-relatedadhesiveprotein (TRAP) gene of Plasmodium falciparum in Thailand. PLoS ONE 9: e90522.


Kawashima M, Ohashi J, Nishida N, Tokunaga K (2012) Evolutionary analysis of classical HLA class I and II genessuggeststhatrecent positive selection acted on DPB1*04:01 in Japanese population. PLoS One 7: e46806.


Hirayasu K, Ohashi J, Kashiwase K, Hananantachai H, Naka I, Ogawa A, Takanashi M, Satake M, Nakajima K, Arase H,Tokunaga K, Patarapotikul J, Yabe T (2012) Significant association of KIR2DL3-HLA-C1 combination with cerebralmalariaandimplications for co-evolution of KIR and HLA. PLoS Pathogens 8: e1002565.


Naka I, Nishida N, Ohashi J (2011) No evidence for strong recent positive selection favoring the 7 repeat allele of VNTRintheDRD4 gene. PLoS One 6: e24410.

 
Ohashi J, Naka I, Tsuchiya N (2011) The impact of natural selection on an ABCC11 SNP determining earwax type.MolecularBiology and Evolution 28: 849-857.


Kimura R, Ohashi J, Matsumura Y, Nakazawa M, Inaoka T, Ohtsuka R, Osawa M, Tokunaga K (2008) Gene FlowandNaturalSelection in Oceanic Human Populations, Inferred from Genome-wide SNP Typing. Molecular Biology andEvolution25: 1750-1761.


Hirayasu K, Ohashi J, Tanaka H, Kashiwase K, Ogawa A, Takanashi M, Satake M, Jia GJ, Chimge NO, Sideltseva EW,TokunagaK, Yabe T (2008) Evidence for natural selection on leukocyte immunoglobulin-like receptors for HLA class IinNortheastAsians. American Journal of Human Genetics 82: 1075-1083.


Fujimoto A, Kimura R, Ohashi J, Omi K, Yuliwulandari R, Batubara L, Mustofa MS, Samakkarn U, Settheetham-Ishida W,IshidaT, Morishita Y, Furusawa T, Nakazawa M, Ohtsuka R, Tokunaga K (2008) A scan for genetic determinants ofhumanhairmorphology: EDAR is associated with Asian hair thickness. Human Molecular Genetics 17: 835-843.


Kimura R*, Fujimoto A, Tokunaga K, Ohashi J (2007) A practical genome scan for population-specific strongselectivesweepsthat have reached fixation. PLoS One 2: e286.


Ohashi J, Naka I, Toyoda A, Takasu M, Tokunaga K, Ishida T, Sakaki Y, Hohjoh H (2006) Estimation of the species-specificmutation rates of the DRB1 locus in human and chimpanzee. Tissue Antigens 68: 427-431.


Hirayasu K, Ohashi J, Kashiwase K, Takanashi M, Satake M, Tokunaga K, Yabe T. (2006) Long-term persistenceofbothfunctional and non-functional alleles at the leukocyte immunoglobulin-like receptor A3 (LILRA3) locussuggestsbalancingselection. Human Genetics 119: 436-443.


Ohashi J, Naka I, Patarapotikul J, Hananantachai H, Brittenham G, Looareesuwan S, Clark AG, Tokunaga K (2004)Extendedlinkage disequilibrium surrounding the hemoglobin E variant due to malarial selection. American Journal ofHumanGenetics74: 1198-1208.


Hohjoh H*, Ohashi J, Takasu M, Nishioka T, Ishida T, Tokunaga K (2003) Recent divergence of the HLA-DRB1*04alleliclineagefrom the DRB1*0701 lineage after the separation of the human and chimpanzee species. Immunogenetics 54:856-861.


Ohashi J, Tokunaga K (2000) Computer simulation analysis suggests weak balancing selection operative at the MICAlocus.Hereditas 131:25-28.


Wu MS, Tani K, Sugiyama H, Hibino H, Izawa K, Tanabe T, Nakazaki Y, Ohashi J, Hohjoh H, Iseki T, Tojo A, NakamuraY,Tanioka Y, Tokunaga K, Asano S (2000) MHC (Major Histocompatibility Complex) -DRB genes and polymorphismsinCommonMarmoset. Journal of Molecular Evolution 51:214-222.


Ohashi J, Tokunaga K (2000) Sojourn times and substitution rate at overdominant and linked neutral loci. Genetics 155:921-927.