KNOWING CHOPS FROM CHUCK - ROASTING MYOD REDUNDANCY

The myf5 and myoD genes are implicated in the specification of vertebr ate skeletal muscle. These genes have been thought to be functionally redundant because neonatal mice bearing homozygous null mutations in e ither gene show grossly normal muscle development, By analyzing the ea rly embryonic develop ment of the mutants, Michael Rudnicki and cowork ers show that trunk muscle development is retarded in embryos bearing myf5 null mutations, while early limb and branchial arch muscle develo pment is retarded by myoD null mutations.' These results indicate that the myoD and myf5 genes are not redundant but that each controls the early specification of distinct muscle cell lineages. BioEssays 20:357 -362, 1998, (C) 1998 John Wiley & Sons, Inc.