Cloning of a novel human nonmuscle alpha-actinin gene and characterization of alpha-actinin expression in nemaline rod myopathy (NRM)
- Children`s Hospital, Boston, MA (United States); and others
The {alpha}-actinins are a group of actin-binding and crosslinking proteins that are evolutionarily related to the spectrins and dystrophin. Muscle isoforms of {alpha}-actinin are localized at the Z-lines where they anchor actin filaments in a constitutive manner. In contrast, nonmuscle (cytoskeletal) isoforms are found in all tissues at adherens type junctions where they may play a role in organizing the actin cytoskeleton. In addition to the previously identified nonmuscle/smooth muscle ACTN1 gene and the skeletal/cardiac isoforms, ACTN2 and ACTN3, we have identified a fourth gene, ACTN4, which maps to chromosome 19q13.1 and is expressed at similar levels in all tissues tested. Sequence analysis reveals that all four human genes are collinear with about 77% amino acid identity overall. The ACTN4 gene is alternatively spliced at the first EF-hand to generate two alternative isoforms, both of which are predicted to be calcium insensitive. By indirect immunofluorescence, ACTN1 and ACTN4 are both expressed in association with the actin cytoskeleton of cultured fibroblasts. Additionally, both are found in vascular smooth muscle, however, ACTN4, but not ACTN1, was also found in some capillaries in skeletal muscle. ACTN2 was found at Z-lines in all muscle fiber types while ACTN3 expression is limited to Z-lines in a subset of fast (Type II) fibers. Interestingly, both ACTN2 and ACTN3 isoforms were identified in nemaline rods from a patient with NRM, suggesting that the genetic mutation responsible for this disorder may not be in an {alpha}-actinin gene.
- OSTI ID:
- 133812
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0545
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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