Cerebral small vessel disease caused by PLOD3 mutation: Expanding the phenotypic spectrum of lysyl hydroxylase-3 deficiency

Skeletal pathology in mouse models of Gould syndrome is partially alleviated by genetically reducing TGFβ signaling

Skeletal defects are hallmark features of many extracellular matrix (ECM) and collagen-related disorders. However, a biological function in bone has never been defined for the highly evolutionarily conserved type IV collagen. Collagen type IV alpha 1 (COL4A1) and alpha 2 (COL4A2) form α1α1α2 (IV) heterotrimers that represent a fundamental basement membrane constituent present in every organ of the body, including the skeleton. COL4A1 and COL4A2 mutations cause Gould syndrome, a variable and clinically heterogenous multisystem disorder generally characterized by the presence of cerebrovascular disease with ocular, renal, and muscular manifestations. We have previously identified elevated TGFβ signaling as a pathological insult resulting from Col4a1 mutations and demonstrated that reducing TGFβ signaling ameliorate ocular and cerebrovascular phenotypes in Col4a1 mutant mouse models of Gould syndrome. In this study, we describe the first characterization of skeletal defects in Col4a1 mutant mice that include a developmental delay in osteogenesis and structural, biomechanical and vascular alterations of mature bones. Using distinct mouse models, we show that allelic heterogeneity influences the presentation of skeletal pathology resulting from Col4a1 mutations. Importantly, we found that TGFβ target gene expression is elevated in developing bones from Col4a1 mutant mice and show that genetically reducing TGFβ signaling partially ameliorates skeletal manifestations. Collectively, these findings identify a novel and unsuspected role for type IV collagen in bone biology, expand the spectrum of manifestations associated with Gould syndrome to include skeletal abnormalities, and implicate elevated TGFβ signaling in skeletal pathogenesis in Col4a1 mutant mice.

Rare Sequence Variation Underlying Suspected Familial Cerebral Small-Vessel Disease

BACKGROUND

Cerebral small-vessel disease (cSVD) is the leading monogenic cause of stroke. Despite genetic screening in routine diagnosis, many cases remain without a known causative variant. Using a cohort with suspected familial cSVD and whole-genome sequencing, we screened for variants in genes associated with monogenic cSVD and searched for novel variants associated with the disease.

METHODS AND RESULTS

Rare variants were identified in whole-genome sequencing data from the NBR (National Institute for Health Research BioResource Rare Disease) study. Pathogenic variants in known monogenic cSVD genes were identified. Gene-based burden tests and family analysis were performed to identify novel variants associated with familial cSVD. A total of 257 suspected cSVD cases (mean ± SD age, 56.2 ± 16.1 years), and 13 086 controls with other nonstroke diseases (5874 [44.9%] men) were studied. A total of 8.9% of the cases carried a variant in known cSVD genes. Excluding these known causes, 23.6% of unrelated subjects with cSVD carried predicted deleterious variants in the Genomics England gene panel, but no association was found with cSVD in burden tests. We identified potential associations with cSVD in noncoding genes, including RP4-568F9.3 (adjusted P = 7.1 × 10-25), RP3-466I7.1 (adjusted P = 8.9 × 10-16), and ZNF209P (adjusted P = 1.0 × 10-15), and matrisomal genes (adjusted P = 5.1 × 10-6), including FAM20C, INHA, LAMC1, and VWA5B2.

CONCLUSIONS

Predicted deleterious variants in known cSVD genes were present in 23.6% of unrelated cases with cSVD, but none of the genes were associated with the disease. Rare variants in noncoding and matrisomal genes could potentially contribute to cSVD development. These genes could play a role in tissue development and brain endothelial cell function. However, further studies are needed to confirm their pathophysiological roles.

Integrated Systems Analysis Deciphers Transcriptome and Glycoproteome Links in Alzheimer's Disease

Glycosylation is increasingly recognized as a potential therapeutic target in Alzheimer's disease. In recent years, evidence of Alzheimer's disease-specific glycoproteins has been established. However, the mechanisms underlying their dysregulation, including tissue- and cell-type specificity, are not fully understood. We aimed to explore the upstream regulators of aberrant glycosylation by integrating multiple data sources using a glycogenomics approach. We identified dysregulation of the glycosyltransferase PLOD3 in oligodendrocytes as an upstream regulator of cerebral vessels and found that it is involved in COL4A5 synthesis, which is strongly correlated with amyloid fiber formation. Furthermore, COL4A5 has been suggested to interact with astrocytes via extracellular matrix receptors as a ligand. This study suggests directions for new therapeutic strategies for Alzheimer's disease targeting glycosyltransferases.