Mouse cDNA encoding for matrilin-4 was cloned and the primary structure of this fourth member of the matrilin family was deduced from the nucleotide sequence. The protein precursor of 624 amino acids consists of a putative signal peptide, two vWFA-like domains linked by four epidermal growth factor-like modules and a potential coiled-coil alpha-helical oligomerization domain at the C-terminus. The predicted Mr of the mature protein is 66 442. Expression in lung, brain, sternum, kidney and heart was detected by Northern blot analysis of mouse mRNA. Additionally an alternatively spliced mRNA lacking the sequence coding for the first vWFA domain was found in 7 weeks old mice leading to a protein precursor of 434 amino acids and a predicted Mr of the mature protein of 45468.