FIG. 2.
The short promoter restricts the Col2a1 enhancer activity in vivo. Schematic (A) and expression (B) of the 8×ECol2a1-NAD1 transgene in comparison with the pattern of P3000i3020Col2a1 (C) driven by the Col2a1 promoter and enhancer (47). (D to N) Histological analysis of 8×ECol2a1-NAD1 cryosections. In the developing limbs (D to I), X-Gal staining is relatively weak in the humerus and radius but sharply increases toward the distal phalanges. LacZ activity is completely repressed or limited to a few cells in the cranial and lumbar vertebral bodies but is high in the caudal ones and in the distal part of nasal bone (nb) (K to N). Expression is highest, limited to groups of cells, in the columnar and prehypertrophic zones, but it is strongly reduced in the source and epiphyseal chondroblasts, except for sporadic staining in the distal epiphysis of the humerus (D to N). t, tarsal; mt, metatarsal. Other abbreviations are as defined for Fig. 1. Bars, 2 mm (B) and 200 μm (D to N).