Defective histogenesis and morphogenesis in the anterior shank skin of the scaleless mutant

Epidermal-dermal tissue interactions between mutant foot skin and normal back skin: a comparison of the inductive capacities of scaleless low line and normal anterior foot dermis

The inductive capacities of 9- to 16-day anterior foot dermis of scaleless low line and normal embryos were compared by recombining them with a common source of epidermis, i.e., 7-day normal back epidermis. Tissue recombinants were cultured as grafts to the chorioallantoic membrane (CAM). Both normal and scaleless low line dermis of 12 to 13 days of incubation began to lose their ability to elicit feather production in 7-day normal back epidermis. Normal foot dermis began to elicit scale production at 12 to 13 days, whereas scaleless low line anterior foot dermis maintained feather production at a low level. It is inferred that without being associated with scale placode formation, scaleless low line anterior foot dermis does not acquire specific inductive capacities related to the production of an outer scale surface in the overlying epidermis. Feather placodes do not function as surrogates of scale placodes. The difference between normal and scaleless low line anterior foot dermis in terms of specific inductive capacities related to scale production is interpreted as a secondary effect of the action of the scaleless allele in interfering with scale placode formation in the scaleless low line anterior foot epidermis.

Abnormal morphagenesis of feather structure and pattern in the chick embryo integument. I. Macroscopic description

The development of feathers in embryos from a profusely feathered line derived from a homozygous scaleless mutant stock was compared with that of embryos from a standard White Leghorn stock. The time of appearance of feather primordia, their structure and their arrangement all were altered in mutant embryos. Unit structures ranging in size from hillocks of 300 mu diameter (the size of normal primordia) to ridges 8 mm long were found in varying numbers in the different tracts of the mutant embryos. the hexagonal pattern characterizing feather primordia in normal embryos was disrupted in scaleless high line embryos. Differential growth and morphogenetic sculpting, as evidenced by the appearance of clefts, generate the form of and subdivide the variable shaped unit structures of the mutant as they elongate. Selection for high feather number was successful in dramatically increasing the total amount of feathering but the absence of coordinate controls of pattern and feather structure development led to the aberrant arrangement of tracts and of structures within the tracts. The basic pattern thus appears to have been destroyed by the scaleless mutation, and the alteration of the phenotype accomplished by selection has not apparently restored its control.

Avian scale development V. Ultrastructure of the chorionic epithelium induced by anterior shank dermis from the scaleless mutant

In combination with dermis from the anterior shank skin of the scaleless mutant, the chorionic epithelium forms an epidermis whose ultrastructural features are indistinguishable from those seen along the inner surface of normal scales and along the anterior shank of the scaleless mutant.

Xenoplastic combinations between chick chorionic epithelium and fetal monkey dermis

Fetel monkey dermis from the sole of the foot or ear induces the chick chorionic epithelum (CE) to form an epidermis that histologically resembles chick rather than monkey. These results support the conclusion that in epithelial-mesenchymal interactions between animals of different vertebrate classes the epithelium responds in a species-specific manner. Differences were noted, however, in the response of the avian CE to either the sole or ear dermis.