Muscle-eye-brain disease (MEB) and Walker Warburg Syndrome (WWS) belong to a spectrum of autosomal recessive diseases characterized by ocular dysgenesis, neuronal migration defects, and congenital muscular dystrophy. Until now, the pathophysiology of MEB/WWS has been attributed to alteration in dystroglycan post-translational modification. Here, we provide evidence that mutations in a gene coding for a major basement membrane protein, collagen IV alpha 1 (COL4A1), are a novel cause of MEB/WWS. Using a combination of histological, molecular, and biochemical approaches, we show that heterozygous Col4a1 mutant mice have ocular dysgenesis, neuronal localization defects, and myopathy characteristic of MEB/WWS. Importantly, we identified putative heterozygous mutations in COL4A1 in two MEB/WWS patients. Both mutations occur within conserved amino acids of the triple-helix-forming domain of the protein, and at least one mutation interferes with secretion of the mutant proteins, resulting instead in intracellular accumulation. Expression and posttranslational modification of dystroglycan is unaltered in Col4a1 mutant mice indicating that COL4A1 mutations represent a distinct pathogenic mechanism underlying MEB/WWS. These findings implicate a novel gene and a novel mechanism in the etiology of MEB/WWS and expand the clinical spectrum of COL4A1-associated disorders.

Long-term survival in WHO grade I meningioma is challenged in patients more than 45 years of age. Excess mortality seems to be associated with both tumor recurrence and stroke. The majority of patients have long-term neurological problems.

Objective Mutations in the type IV collagen alpha 1 gene (COL4A1) cause dominantly inherited cerebrovascular disease. We seek to determine the extent to which COL4A1 mutations contribute to sporadic, non-familial, intracerebral hemorrhages (ICHs). Methods We sequenced COL4A1 in 96 patients with sporadic ICH. The presence of putative mutations was tested in 145 ICH–free controls. The effects of rare coding variants on COL4A1 biosynthesis were compared to previously validated mutations that cause porencephaly, small vessel disease and HANAC syndrome. Results We identified two rare non–synonymous variants in ICH patients that were not detected in controls, two rare non–synonymous variants in controls that were not detected in patients and two common non–synonymous variants that were detected in patients and controls. No variant found in controls affected COL4A1 biosynthesis. Both variants (COL4A1P352L and COL4A1R538G) found only in patients changed conserved amino acids and impaired COL4A1 secretion much like mutations that cause familial cerebrovascular disease. Interpretation This is the first assessment of the broader role for COL4A1 mutations in the etiology of ICH beyond a contribution to rare and severe familial cases and the first functional evaluation of the biosynthetic consequences of an allelic series of COL4A1 mutations that cause cerebrovascular disease. We identified two putative mutations in 96 patients with sporadic ICH and show that these and other previously validated mutations inhibit secretion of COL4A1. Our data support the hypothesis that increased intracellular accumulation of COL4A1, decreased extracellular COL4A1, or both, contribute to sporadic cerebrovascular disease and ICH.

Mutations in the type IV collagen alpha 1 gene (COL4A1) cause Cerebrovascular Diseases (CVDs) in mice and human patients. Patients with COL4A1 mutations suffer from a broad range of CVDs, from infantile porencephaly to debilitating or fatal intracerebral hemorrhage (ICH), to subclinical cerebral microbleeds, suggesting that environmental and other genetic factors may influence their phenotypes. COL4A1 is one of the most abundant proteins in basement membranes and forms heterotrimers with COL4A2. Among possible pathogenic mechanisms are cellular stress due to the toxic intracellular aggregation of the COL4A1 and COL4A2 proteins and/or their absence in the basement membrane. Our first goal is to identify the relative contributions of COL4A1 and COL4A2 mutations to sporadic ICH and to understand the cellular mechanisms and genetic complexity underlying the disease. We identified novel COL4A1 mutations and for the first time, we discovered COL4A2 mutations in a cohort of 96 patients with sporadic ICH. Using a cell-based assay we determined that the mutations impair COL4A1 and COL4A2 secretion. We showed that mutant COL4A1 or COL4A2 proteins accumulate within the cell where they titrate normal COL4A1 and COL4A2 proteins. Interestingly, we found that some of the mutations can ultimately result in endoplasmic reticulum (ER) stress and activation of the Unfolded Protein Response. Our second goal was to test the hypothesis that differences in genetic context could contribute to phenotypic variability in human patients. Thus, we characterized CVD in Col4a1 mutant mice with two different genetic backgrounds. Using cerebral magnetic resonance imaging and histological analysis, we show that one or more genetic modifiers from the CAST/EiJ strain significantly reduce the size and frequency of ICHs detected in Col4a1 mutant mice on a C57BL/6J background. In conclusion, we found that both COL4A1 and COL4A2 mutations cause ICH in human patients, our results support that ER stress could be involved in the pathogenesis and we showed that genetic context is crucial for expressivity and severity of the CVD. We predict that ongoing experiments to better understand the cell biology of COL4A1 and COL4A2 mutations and the mechanisms of genetic modification could lead to targeted therapeutics to reduce the risk of CVD in patients with COL4A1 or COL4A2 mutations.