Storrs Scaleless

Origin & History: Found in New Hampshire flock, Abbott, UK & Asmundson, VS 1957 J Hered 48:63-70; received from Abbott in 1965.

Breed: New Hampshire background

Symbol: sc

Characteristics: Autosomal recessive

Description: Nearly complete lack of down feathers at hatch; does not form scutate scales or most feathers, and forms defective spurs and reticulate scales. Conjunctivival papillae and scleral ossicles are reduced in number and morphologically abnormal.

           scaleless hen

Additional Information: Epidermal placode formation, an initial step in formation of scutate but not reticulate scales, does not occur in scaleless (sc) anterior shank skin. (J Exp Zool 181:365-384, 1972a; ibid, 181:385-408, 1972b).An alpha stratum (alpha-keratin), typical of the inner surface of the scutate scale, develops but a beta stratum (beta- or feather-type keratin), characteristic of the outer scale surface of normal scutate scales, does not. (J Exp Zool 190:71-78, 1974; Dev Bio 46:436-438, 1975) Morphogenesis of reticulate scales (footpads) is disrupted, since irregular crevices are formed in place of normal scales, but epidermal differentiation in the crevices is similar to that of reticulate scales and alpha-keratin is present. (Dev Biol 68:1-15, 1979a; J Morphol 161:111-122, 1979b; ibid. 166:197-202, 1980) Normal reticulate scale formation does not involve epidermal placodes. (J Morphol. 154:83-94, 1977) Reciprocal epidermal-dermal tissue recombinations between sc and normal embryonic skin have showed that the initial defect is ectodermal, centering around the tissue interactions through which scale or feather-inducing capacity is conferred on the embryonic dermis.The critical period for scale formation is between stages 36 and 38 (10-12 days) and involves developmental events associated with formation of epidermal placodes and the first appearance of scale ridges.Normal anterior shank dermis acquires its ability to induce scutate scale formation at this time.sc dermis that maintains contact with sc epidermis does not receive the cues needed to acquire scale-inducing ability.Developmentally younger sc dermis is competent to accept cues from normal anterior shank epidermis and acquire scale-inducing ability; developmentally older sc is not.(J Exp Zool 154:7-19, 1963; J Hered 54:254-262, 1963; J Exp Zool 200:125-136, 1977; J Exp Zool 181:99-110, 1972; ibid. 191:133-139, 1975; J Exp Zool 207:505-512, 1979; Science 214:1033-1034, 1981; Dev Biol 89:493-502, 1982; ibid. 105:343-350, 1984) Exposure for 3-5 days in culture to heparin beads loaded with FGF-2 can induce feather germ formation in stage 33 scaleless backskin. (Proc Nat Acad Sci 93:10246-10249, 1996) Rescue of feather formation in sc skin by FGF treatment has been confirmed and roles in early feather formation in normal skin have also been indicated for Bmp-2, Delta-1, beta-catenin, Shh and Wnt-7a. (Mech Dev 72:159-168, 1998; Development 125:3775-3787, 1998; ibid. 126:3509-3521, 1999; Dev Biol 201:1-12, 1998; Dev Biol 219:98-114, 2000) Expression of genes associated with scale and feather production has been compared in sc and normal embryos for the following:

(Dev Biol 116: 15-22, 1986; Curr. Topic Dev Biol 22:235-253, 1987; Differentiation 38:115-123, 1988; Dev Dyn 196:283-290, 1993): beta-keratin

(Dev Biol 147:174-186, 1991; J Exp Zool 269:349-366): Tenascin

(Dev Dyn 200:L129-143, 1994): beta-1 integrin

(Proc Nat Acad Sci 93:10246-10249, 1996): Fgf-2, FGFR-1

(Dev Dyn 207:157-170, 1996): Shh

(Mech Dev 72:159-168, 1998): C-Delta-1

(Dev Biol 219:98-114, 2000): beta-catenin, Msx-1, LEF-1, APC