Characterization of novel Col5a3 knockout and Tll1 conditional knockout mice

Collagens constitute the most abundant grouping of extracellular proteins in the body, and 29 different collagen types exist. Fibrillar collagens comprise the major fibrous components of vertebrate extracellular matrix (ECM). To date, heritable diseases have been associated with defects in all fibrillar collagen chains, with the exception of the alpha3 chain of type V collagen [alpha3(V)]. BMP1/TLD-like proteinases proteolytically cleave precursor forms of several collagen molecules in an important step in collagen biosynthesis. Work described herein details characterization of two novel transgenic knockout mouse lines in which the gene for either the alpha3(V) chain or for the BMP1/TLD-like proteinase mTLL1 has been ablated. Study of such mice is likely to fill gaps in our knowledge of in vivo functions of collagens and collagen processing enzymes.;Col5a3 knockout mice, lacking the alpha3(V) chain, exhibit gender-specific differences in adipose deposition and cardiovascular function. Female Col5a3 knockouts displayed reduced thickness of hypodermal adipose deposits as well as resistance to diet-induced obesity compared to controls. Male Col5a3 knockouts were severely exercise-intolerant and aortae from these animals were less compliant than those of wild type controls Analysis of collagen fibril diameter from Col5a3-/- tendons provided the first demonstration of regulation of collagen fibril diameter by the alpha3(V) chain. The viability and unique collection of phenotypic traits displayed by Col5a3 -/- mice suggest the possibility of naturally occurring mutations in the COL5A3 gene and phenotypic consequences in the general human population.;In addition to cleaving procollagens, BMP1/TLD-like proteinases have also been shown to cleave a variety of other substrates. Such cleavage includes biosynthetic processing of additional ECM-related proteins and proteolytic activation of various growth factors. The physiological importance of the BMP1/TLD-like proteinase mTLL1 is underscored by the embryonic lethality of mice null for the mTLL1 gene (Tll1). Nervous system-specific Tll1 knockout mice were produced in order to assess the function of the proteinase mammalian tolloid-like 1 (mTLL1) in this tissue. Phenotypic characterization revealed no defects in brain morphology, motor function, locomotion, or emotionality in Tll1 conditional knockouts. However, apparatus-specific deficits in these mice were observed in behavioral learning tasks.