Genomic structure, mapping, activity and expression of fibroblast growth factor 17.

Fibroblast growth factors are essential molecules for development. Here we characterize Fgfl7, a new member of the fibroblast growth factor (FGF) family. The Fgfl7 gene maps to mouse chromosome 14 and is highly conserved between mouse and human (93% identity). It exhibits 60% amino acid identity with Fgf8 and 50% identity with Fgf8. Both Fgf8 and Fgf17 have a similar structure and a similar pattern of alternative splicing in the 5' coding region. When expressed in 3T3 fibroblasts, mouse FGF17 is transforming, indicating that it can activate the 'c' splice form of either FGF receptor (FGFR) one or two. During midgestation embryogenesis, in situ hybridization analysis localized Fgf17 expression to specific sites in the midline structures of the forebrain, the midbrain-hindbrain junction, the developing skeleton and in developing arteries. Comparison to Fgf8 revealed a striking similarity in expression patterns, especially in the central nervous system (CNS), suggesting that both genes may be important for CNS development, although Fgf17 is expressed somewhat later than Fgf8. In the developing skeleton, both genes are expressed in costal cartilage while Fgf8 is preferentially expressed in long bones. In the developing great vessels Fgfl7 is preferentially expressed, suggesting that it may have a more prominent role in vascular growth.     

Genomic structure and chromosomal mapping of the murine CD40 gene.

The B cell-associated surface molecule, CD40, is likely to play a central role in the expansion of Ag-stimulated B cells, and their interaction with activated Th cells. In our study we have isolated genomic clones of murine CD40 from a mouse liver genomic DNA library. Comparison with the murine CD40 cDNA sequence revealed the presence of nine exons that together contain the entire murine CD40 coding region, and span approximately 16.3 kb of genomic DNA. The intron/exon structure of the CD40 gene resembles that of the low affinity nerve growth factor receptor gene, a close homolog of both human and murine CD40. In both cases the functional domains of the receptor molecules are separated onto different exons throughout the genes. Southern blot analysis demonstrated that murine CD40 is a single copy gene that maps in the distal region of mouse chromosome 2.