Characterization of a new human isoform of the enigma homolog family specifically expressed in skeletal muscle.

We have identified a fourth member of the enigma homolog (ENH) family within a pool of human transcripts specifically expressed in skeletal muscle tissue. This new ENH isoform of 215 amino acids is the shorter of the family, it lacks the C-terminal LIM domains present in ENH1 but contains the N-terminal PDZ domain. Northern blot analysis confirmed the muscle specificity of ENH4. Western blot studies of muscle tissues using a non-isoform-specific anti-ENH antibody revealed that ENH4 is present only in skeletal muscle and that there is a specific distribution of ENH members between skeletal and cardiac muscles, which is different in human and mouse. ENH4 was found to co-localize in the sarcomeric Z-band and to interact with alpha-actinin like the other members of the ENH family. Two additional new ENH4 partners of about 34 and 54kDa were also identified. These results bring new lights on the ENH protein family members.