{"id":1329,"date":"2013-02-27T23:47:39","date_gmt":"2013-02-27T23:47:39","guid":{"rendered":"http:\/\/www.ealc.info\/de\/?p=1329"},"modified":"2021-06-14T06:23:02","modified_gmt":"2021-06-14T06:23:02","slug":"die-sache-mit-dem-merle-gen","status":"publish","type":"post","link":"https:\/\/www.ealc.info\/cs\/otazka-merle-genu\/","title":{"rendered":"Ot\u00e1zka merle genu"},"content":{"rendered":"

<\/p>\n

\"\"<\/a>A\u010dkoliv se typick\u00fd merle vzor, tj. srst s v\u00fdskytem r\u016fzn\u011b velk\u00fdch a nepravideln\u00fdch ploch \u0159ed\u011bn\u00fdch a koncentrovan\u00fdch barev, objevuje u \u0159ady zn\u00e1m\u00fdch plemen, jako je nap\u0159. kolie, border kolie, \u0161eltie, australsk\u00fd ov\u010d\u00e1k, jezev\u010d\u00edk, atd., netvo\u0159\u00ed obvykle takto zbarven\u00ed jedinci v\u011bt\u0161inu populace t\u011bchto plemen. Je tomu tak nejsp\u00ed\u0161 proto, \u017ee u t\u011bchto plemen je spojen\u00ed obou merle zbarven\u00fdch rodi\u010d\u016f zak\u00e1z\u00e1no chovatelsk\u00fdmi \u0159\u00e1dy nebo se b\u011b\u017en\u011b nedoporu\u010duje. D\u016fvodem je hlavn\u011b to, \u017ee z takov\u00fdch spojen\u00ed se \u010dasto rod\u00ed jedinci s p\u0159evahou b\u00edl\u00e9 barvy a \u010dasto s \u0159adou mo\u017en\u00fdch zdravotn\u00edch defekt\u016f, kter\u00e9 s takov\u00fdm zbarven\u00edm souvis\u00ed.<\/p>\n

Louisiansk\u00fd leopard\u00ed pes (Louisiana Catahoula, LC) se takov\u00fdm zbarven\u00edm naopak py\u0161n\u00ed. Spojov\u00e1n\u00ed rodi\u010d\u016f s merle\/leopard\u00edm zbarven\u00edm je proto \u00fa\u010delov\u00e9 a ani v\u00fdskyt n\u011bkter\u00fdch typick\u00fdch defekt\u016f, spojovan\u00fdch s p\u0159\u00edtomnost\u00ed merle genu, kter\u00fd toho zbarven\u00ed zp\u016fsobuje, v\u011bt\u0161inu chovatel\u016f LC v zemi p\u016fvodu, USA, neodrazuje. Nen\u00ed proto divu, \u017ee v\u011bt\u0161ina populace LC tento gen ve sv\u00e9 genov\u00e9 v\u00fdbav\u011b nese a \u017ee \"\"<\/a>jednobarevn\u00fdch\/celobarevn\u00fdch\/solid jedinc\u016f, kte\u0159\u00ed nejsou jeho nosi\u010di, je v tomto p\u0159\u00edpad\u011b men\u0161ina. P\u0159itom se v\u0161ak nezd\u00e1, \u017ee by toto plemeno t\u00edmto stavem n\u011bjak v\u00fdrazn\u011b str\u00e1dalo a v\u00fdskyt defekt\u016f byl \u0159\u00e1dov\u011b vy\u0161\u0161\u00ed ne\u017e u ostatn\u00edch plemen s merle genem.<\/p>\n

Merle gen (nebo l\u00e9pe \u0159e\u010deno gen, kter\u00fd je za toto zbarven\u00ed zodpov\u011bdn\u00fd) se poda\u0159ilo kolektivu v\u011bdc\u016f, pod veden\u00edm Leigh Ann Clark, ur\u010dit v r. 2006 (Clark et al. 2006, PNAS 103 (5): 1376-81). Byl to pr\u016flom, kter\u00fd kone\u010dn\u011b umo\u017enil testovat ps\u00ed populace i z tohoto hlediska. Prok\u00e1zali, \u017ee t\u00edm, ji\u017e n\u011bjakou dobu hledan\u00fdm, genem je SILV (Silver-locus, \"\"<\/a>Pmel17). Tento gen pat\u0159\u00ed mezi geny zn\u00e1m\u00e9 t\u00edm, \u017ee \u0159ed\u00ed barvu srsti a jeho exprese se projevuje v\u00fdlu\u010dn\u011b v oblasti k\u016f\u017ee a o\u010d\u00ed. Zjistilo se, \u017ee genetick\u00e9 zm\u011bny (mutace) v oblasti SILV genu ovliv\u0148uj\u00ed norm\u00e1ln\u00ed funkci tohoto genu tak, \u017ee v\u00fdsledkem je vzor srsti s oblastmi a skvrnami \u0159ed\u011bn\u00e9ho pigmentu sm\u00edchan\u00e9 s norm\u00e1ln\u00edm pigmentem ne\u0159ed\u011bn\u00fdm. Nemodifikovanou verzi SILV genu ozna\u010dujeme m,<\/strong> zat\u00edmco modifikovan\u00e9 verze jsou ozna\u010dov\u00e1ny M<\/strong> (tzn. merle gen). Zm\u011bny (modifikace) SILV genu jsou zp\u016fsobeny inserc\u00ed (vlo\u017een\u00edm) mobiln\u00edho genov\u00e9ho elementu, zvan\u00e9ho retrotransposon, kter\u00fd m\u016f\u017ee m\u00edt, jak se dnes ukazuje, r\u016fznou d\u00e9lku. Zd\u00e1 se, \u017ee d\u00e9lka t\u00e9to vsunut\u00e9 sekvence, m\u00e1 tak\u00e9 vliv na to, jak\u00fdm zp\u016fsobem se modifikace projev\u00ed ve fenotypu psa.<\/p>\n

\"\"<\/a>Typick\u00fd M<\/strong> gen obsahuje insertn\u00ed sekvenci o d\u00e9lce 259-262 bp a projevuje se zn\u00e1m\u00fdm merle\/leopard\u00edm zbarven\u00edm u ps\u016f, kte\u0159\u00ed jsou heterozygoti (mM<\/strong>), a typick\u00fdm double merle fenotypem s p\u0159evahou b\u00edl\u00e9 barvy u homozygot\u016f (MM<\/strong>). Druh\u00e1 modifikace, popsan\u00e1 v p\u016fvodn\u00edm \u010dl\u00e1nku, obsahuje krat\u0161\u00ed verzi insertu o d\u00e9lce ca 220 – 225 bp. Tato modifikace se v barv\u011b srsti viditeln\u011b neprojevuje, a proto byla nazv\u00e1na \u201eskryt\u00e9 merle\u201c (cryptic, phantom) a zna\u010d\u00ed se Mc. Heterozygotn\u00ed i homozygotn\u00ed jedinci (tj. mMc<\/strong>, a nejsp\u00ed\u0161 tak\u00e9 McMc<\/strong>) vypadaj\u00ed jako jednobarevn\u00ed\/solid, stejn\u011b jako homozygotn\u00ed jedinci s nemodifikovan\u00fdm genem (mm<\/strong>) ve sv\u00e9 genetick\u00e9 v\u00fdbav\u011b. Odli\u0161it je lze pouze genetick\u00fdmi testy.<\/p>\n

\"\"<\/a><\/p>\n

Ob\u011b tyto varianty byly pops\u00e1ny u v\u0161ech studovan\u00fdch plemen a jejich d\u011bdi\u010dnost je autosom\u00e1ln\u00ed a ne\u00fapln\u011b dominantn\u00ed. Od ka\u017ed\u00e9ho z rodi\u010d\u016f z\u00edsk\u00e1v\u00e1 potomek 1 alelu tohoto genu a rozlo\u017een\u00ed v\u00fdsledn\u00fdch genotyp\u016f se \u0159\u00edd\u00ed klasickou Mendelovskou genetikou.<\/p>\n

\u201eLeopard\u00ed\u201c merle gen prok\u00e1zalo ned\u00e1vn\u00e9 d\u016fkladn\u011bj\u0161\u00ed testov\u00e1n\u00ed merle genu u populace LC. Byla toti\u017e detekov\u00e1na dal\u0161\u00ed modifikace SILV genu, insertem o d\u00e9lce 243- 249 bp, kter\u00e1 se u ostatn\u00edch plemen zat\u00edm neprok\u00e1zala. Pro zjednodu\u0161en\u00ed a odli\u0161en\u00ed od obou v\u00fd\u0161e zm\u00edn\u011bn\u00fdch typ\u016f pou\u017e\u00edv\u00e1m d\u00e1le pracovn\u00ed n\u00e1zev Ma<\/strong>. D\u00e9lka vsunut\u00e9 sekvence v SILV genu je n\u011bco mezi norm\u00e1ln\u00ed MaMc<\/strong> a ve fenotypu se projevuje m\u00e9n\u011b v\u00fdrazn\u011b ne\u017e M<\/strong>, ale v\u00edce ne\u017e Mc<\/strong>. Heterozygoti Ma (tj. mMa<\/strong>) se rod\u00ed jako celobarevn\u00ed\/solid, ale zd\u00e1 se, \u017ee se vzr\u016fstaj\u00edc\u00edm v\u011bkem psa, se merle vzor v srsti st\u00e1v\u00e1 v\u00fdrazn\u011bj\u0161\u00ed a patrn\u011bj\u0161\u00ed. Homozygoti, tj. MaMa, maj\u00ed obvykle merle vzor, av\u0161ak v\u0161e v \u0159ed\u011bn\u00fdch barv\u00e1ch, tj. zejm\u00e9na modr\u00e1 a nejsp\u00ed\u0161 i dal\u0161\u00ed \u0159ed\u011bn\u00e9 barvy, ale nejsou p\u0159ev\u00e1\u017en\u011b b\u00edl\u00ed. Kombinace Ma a norm\u00e1ln\u00edho M<\/strong>, tj. \"\"<\/a>MaM, d\u00e1v\u00e1 fenotyp, kter\u00e9mu \u0159\u00edk\u00e1me patchwork, kde se st\u0159\u00eddaj\u00ed v\u011bt\u0161\u00ed plochy r\u016fzn\u00fdch barev s leopard\u00edm vzorem a tak\u00e9 plochami b\u00edl\u00e9 barvy. Heterozygoti McMa<\/strong> vypadaj\u00ed tak\u00e9 sp\u00ed\u0161 jako jednobarevn\u00ed.<\/p>\n

P\u0159\u00edtomnost LC specifick\u00e9 modifikace SILV genu, tj. Ma<\/strong>, vysv\u011btluje p\u0159\u00edpady, kdy se ze solid zbarven\u00fdch rodi\u010d\u016f narod\u00ed potomci leopard\u00edch barev a vzor\u016f. Podle na\u0161ich dosavadn\u00edch poznatk\u016f, se p\u0159\u00edtomnost Mc<\/strong> bez genetick\u00e9 anal\u00fdzy rozeznat podle fenotypu ned\u00e1.<\/p>\n

V t\u00e9to chv\u00edli a za na\u0161ich sou\u010dasn\u00fdch znal ost\u00ed to vypad\u00e1, \u017ee pro vysv\u011btlen\u00ed odli\u0161n\u00e9ho chov\u00e1n\u00ed merle genu u LC nejsou t\u0159eba \u017e\u00e1dn\u00e9 dal\u0161\u00ed nezn\u00e1m\u00e9 geny. Nicm\u00e9n\u011b<\/p>\n

\"\"<\/a>

„patchwork“ – Genotyp MaM<\/p><\/div>\n

regulace, modifikace a vz\u00e1jemn\u00e9 ovlivn\u011bn\u00ed dal\u0161\u00edmi geny nem\u016f\u017eeme ani zcela vylou\u010dit, dokud nebude zn\u00e1mo v\u00edce informac\u00ed o mechanismech exprese tohoto modifikovan\u00e9ho genu, d\u011bdi\u010dnosti r\u016fzn\u00fdch d\u00e9lek SINE a p\u0159\u00edpadn\u00e9 p\u0159\u00edtomnosti a efektech dal\u0161\u00edch gen\u016f. M\u016f\u017ee tu hr\u00e1t i ur\u010ditou roli nap\u0159. piebald gen, kter\u00fd n\u011bkte\u0159\u00ed LC ur\u010dit\u011b tak\u00e9 maj\u00ed a kter\u00fd m\u016f\u017ee zvy\u0161ovat mno\u017estv\u00ed b\u00edl\u00e9 barvy srsti.<\/p>\n

Stanoven\u00ed merle genu prov\u00e1d\u00ed firma Biofocus v N\u011bmecku. Metodika je zalo\u017eena na anal\u00fdze PCR produkt\u016f podle specifick\u00fdch primer\u016f. Pro anal\u00fdzu je nutno izolovat z v\u00fdchoz\u00edho materi\u00e1lu DNA. Praxe ukazuje, \u017ee spolehliv\u011bj\u0161\u00edm v\u00fdchoz\u00edm materi\u00e1lem je mal\u00e9 mno\u017estv\u00ed krve.<\/p>\n

\"\"<\/a>Dosavadn\u00ed v\u00fdsledky potvrzuj\u00ed, \u017ee LC je plemeno \u201epromo\u0159en\u00e9\u201c merle genem. Uk\u00e1zalo se, \u017ee v\u00edce ne\u017e 80 % testovan\u00fdch jedinc\u016f bylo nosi\u010dem n\u011bjak\u00e9 formy merle genu. Z tohoto po\u010dtu bylo v\u00edce ne\u017e 30 % double merle n\u011bjak\u00e9ho typu a v\u00edce ne\u017e 30 % vypadalo jako solid.<\/p>\n

Napsala RNDr. Helena Synkov\u00e1<\/p>\n

\n

<\/p>","protected":false},"excerpt":{"rendered":"

Leider ist der Eintrag nur auf Angli\u010dtina (Usa) verf\u00fcgbar.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[7],"tags":[],"_links":{"self":[{"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/posts\/1329"}],"collection":[{"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/comments?post=1329"}],"version-history":[{"count":39,"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/posts\/1329\/revisions"}],"predecessor-version":[{"id":4267,"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/posts\/1329\/revisions\/4267"}],"wp:attachment":[{"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/media?parent=1329"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/categories?post=1329"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.ealc.info\/cs\/wp-json\/wp\/v2\/tags?post=1329"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}