Mutation in the Trapalpha/Ssr1 gene, encoding translocon-associated protein alpha, results in outflow tract morphogenetic defects.
Translocon-associated protein complex (TRAP) is thought to be required for efficient protein-specific translocation across the endoplasmic reticulum membrane. We created a mutation in the Trapalpha gene that leads to the synthesis of a truncated TRAPalpha protein fused to ShBle-beta-galactosidase. Analysis of Trapalpha cDNAs reveals that among three different messenger RNAs expressed in the mouse, one of them encodes a slightly larger protein that differs in its C-terminal end. This mRNA, specific for skeletal muscle and heart, is only expressed after birth. Homozygous Trapalpha mutant pups die at birth, likely as a result of severe cardiac defects. Indeed, the septation of the proximal part of the outflow tract is absent, resulting in a double-outlet right ventricle. Studies of protein secretion in transfected embryonic fibroblasts reveal that the TRAP complex does not function properly in homozygous mutant cells and confirm, in vivo, the involvement of TRAP in substrate-specific translocation. Our results provide the first in vivo demonstration that a member of the TRAP complex plays a crucial role in mammalian heart development and suggest that TRAPalpha could be involved in translocation of factors necessary for maturation of endocardial cushions.
Mesbah
K
K
Laboratoire EGDM, CNRS URA 2578, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, France.
Camus
A
A
Babinet
C
C
Barra
J
J
D000375:Aging / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002465:Cell Movement; D017124:Conserved Sequence; D018076:DNA, Complementary / Q000235:genetics / Q000302:isolation & purification; D004622:Embryo, Mammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D006321:Heart / Q000196:embryology; D006720:Homozygote; D006801:Humans; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009206:Myocardium / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D018000:Receptors, Peptide / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017385:Sequence Homology
D002135:Calcium-Binding Proteins; D018076:DNA, Complementary; D008562:Membrane Glycoproteins; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D018000:Receptors, Peptide; D011993:Recombinant Fusion Proteins; C066973:signal sequence receptor; D006026:Glycoside Hydrolases; C089138:beta-galactanase