A model system for polydactyly; The Korean Ogye

다국어 초록 (Multilingual Abstract)

Polydactyly, the addition of one or more extra digits, occurs in various vertebrates as well as in humans with prevalence ranging from 5 to 19 per 10,000 live births1,2). This common malformation has a genetic cause and was one of the earliest genetic mutations studied in chicken3). Furthermore, polydactyly relates to the phenotype found in many domestic chicken breeds including Dorking, Silkie, and Sultan. Autosomal inheritance is shown in polydactyly of chicken with incomplete penetrance 4). One proposal is that it is controlled by more than one gene5).
Sonic hedgehog (Shh) is a principal master regulator determining the digit number and identity in the vertebrate limbs. Shh is expressed in posterior region of mesenchyme, known as the zone of polarizing activity (ZPA) in the limb bud. Shh is a key morphogen at the anterior-posterior limb axis in early embryogenesis6,7). Intrinsic regions of Lmbr1 (a ZPA regulatory sequence, ZRS), which is located 1Mb upstream of Shh, regulate Shh expression in the ZPA. Mutations in intron3 of LMBR1 are associated with ectopic Shh expression in the limb and / or polydactyly in chickens7-10). Along with this, deletion of intron 5 of LMBR1 (1654 bp) causes oligozeugodactyly (loss of posterior element of zeugopod along with all digits except digit1 in the leg) for Silkie11). The Silkie has polydactylous feet and expresses ectopic Shh as well as the expression of genes downstream of Shh signaling, Hoxd13 and Bmp2, in the anterior leg bud from stage 25 Hamburger and Hamilton (HH) stages12).
Korean Ogye, which has been mis-named as Korean Native Ogol chickens, is a species protected by the Korean government (Protected Species Act No. 265), and has been studied at genetic and population levels13-15). Korean Ogye has black feathers, as well as black bones, skin, eye, and claws. It has been known that purebred of Korean Ogye has four toes with no fine furs, whereas mixed Korean Ogye expresses polydactyly with 5-6 toes with fine furs. This study aims to reveal the phenotype and genetic expressions related to Korean Ogye polydactyly.

참고문헌 (Reference)

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