N-RAP expression during mouse heart development.
N-RAP gene expression and N-RAP localization were studied during mouse heart development using semiquantitative reverse transcriptase-polymerase chain reaction and immunofluorescence. N-RAP mRNA was detected at embryonic day (E) 10.5, significantly increased from E10.5 to E16.5, and remained essentially constant from E16.5 until 21 days after birth. In E9.5-10.5 heart tissue, N-RAP protein was primarily associated with developing premyofibril structures containing alpha-actinin, as well as with the Z-lines and M-lines of more-mature myofibrils. In contrast, N-cadherin was concentrated in patches at the periphery of the cardiomyocytes. N-RAP labeling markedly increased between E10.5 and E16.5; almost all of the up-regulated N-RAP was associated with intercalated disk structures, and the proportion of mature sarcomeres containing N-RAP decreased. In adult hearts, specific N-RAP staining was only observed at the intercalated disks and was not found in the sarcomeres. The results are consistent with N-RAP functioning as a catalytic scaffolding molecule, with low levels of the scaffold being sufficient to repetitively catalyze key steps in myofibril assembly.
Lu
Shajia
S
Laboratory of Muscle Biology, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Department of Health and Human Services, Bethesda, MD 20892, USA.
Borst
Diane E
DE
Horowits
Robert
R
D000185:Actinin / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D006321:Heart / Q000196:embryology* / Q000502:physiology; D051379:Mice; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D012333:RNA, Messenger / Q000378:metabolism
D015820:Cadherins; D009124:Muscle Proteins; C491567:Nrap protein, mouse; D012333:RNA, Messenger; D000185:Actinin