May act as a cross-bridge between fibrils and other extracellular matrix molecules. Involved in skeletal myogenesis in the developing esophagus. May play a role in organization of the pericellular matrix or the sphinteric smooth muscle. Oligomer; disulfide-linked. Expressed in the myotome of somites from 9.5 dpc. In muscular tissues, expression is transient and is confined to a few sites of the developing embryo, such as limbs, tongue, and smooth muscle layers of stomach and esophagus. Also detected in skin at 16.5 dpc and in cerebral cortex and hippocampus of the newborn brain. In adult, expression is only observed in cerebrum, cerebellum, eyes, and testis. In CNS, expression gradually increases following birth. Also expressed in embryonic fibroblasts and to a lesser extent in adult fibroblasts. The numerous interruptions in the triple helix may make this molecule either elastic or flexible. Prolines at the third position of the tripeptide repeating unit (G-X-Y) are hydroxylated in some or all of the chains. Mice show severe signs of malnourishment and the majority die within the first three weeks of postnatal life. Newborn homozygotes do not show gross anatomical abnormalities, except for smaller size of the internal organs. However, necroscopy of the mice that survive past the weaning stage reveals a dilated esophagus (megaesophagus) with retention of ingesta immediately above the diaphragm level. Mutant mice also exhibit an additional defect, namely impaired smooth-to-skeletal muscle cell transdifferentiation in the abdominal segment of the esophagus. Heterozygotes by comparison are morphologically normal, viable and fertile. Belongs to the fibril-associated collagens with interrupted helices (FACIT) family.