Biglycan

Biglycan (BGN) is a proteoglycan protein involved in collagen fiber assembly (UniProt: P21810). It is a small leucine-rich proteoglycan with a molecular mass of approximately 41.7 kDa and is expressed as a 368-amino-acid protein in humans. Beyond its structural role in extracellular matrix organization, biglycan mutations cause rare skeletal and cardiovascular disorders including Meester-Loeys syndrome and X-linked spondyloepimetaphyseal dysplasia (UniProt: P21810).

Biglycan is relevant to Alzheimer's disease pathology. In post-mortem AD brain tissue compared to age-matched controls, biglycan protein levels are significantly elevated, with a mean log2 fold-change of 1.34 across multiple subcellular fractions (P2, P3, S2, S3) measured by tandem mass spectrometry (Chaparral AD proteomics). This upregulation suggests that biglycan accumulation or altered deposition may be associated with AD neuropathology, though the precise functional contribution remains to be elucidated.