Db. Constam et al., SPC4, SPC6, AND THE NOVEL PROTEASE SPC7 ARE COEXPRESSED WITH BONE MORPHOGENETIC PROTEINS AT DISTINCT SITES DURING EMBRYOGENESIS, The Journal of cell biology, 134(1), 1996, pp. 181-191
In the present study, we screened for subtilisin-like proprotein conve
rtases (SPCs) that potentially regulate the activation of known growth
factors during embryonic development. We isolated a novel protease, S
PC7, as well as several known SPCs. SPC7, like SPC1, is expressed ubiq
uitously throughout development. In contrast, SPC4 and SPC6 exhibit dy
namic expression patterns. SPC4 transcripts were initially detected in
the granulosa cells of secondary follicles, Shortly after implantatio
n, SPC4 transcripts are localized to extraembryonic cell populations,
and at later stages are detected in discrete tissues including the pri
mitive gut, heart, neural tube, and limb buds. Within the limb buds, S
PC4 mRNA is most abundant in the apical ectodermal, ridge (AER). At la
ter stages of limb development, SPC4 mRNA is strongly expressed in car
tilage and in the interdigital mesenchyme. In contrast, high SPC6 mRNA
levels are detected in somites, the dorsal surface ectoderm, and in v
ertebral cartilage primordia, In limb buds, SPC6 is strongly expressed
in the AER, and at later stages in dorsal mesenchyme. A comparison of
these expression patterns with those of several bone morphogenetic pr
oteins (BMPs) indicates that processing of these growth factors may be
limited by the local availability of SPCs.