Recently, mutations affecting a microRNA-29 (miR-29)-binding site in the 3'-untranslated region of COL4A1 have been identified as a cause of pontine autosomal dominant microangiopathy with leukoencephalopathy (PADMAL) and hereditary multi-infarct dementia (hMID) of the Swedish type. PADMAL and Swedish hMID are extremely rare disorders with no de novo mutations previously reported. A patient with cerebral small vessel disease underwent comprehensive neurological examinations, neuroimaging analysis, and whole-exome sequencing. Co-segregation analysis was performed on his family, and haplotype analysis was conducted to confirm the biological relationship. The patient experienced recurrent ischemic strokes since age 32. Brain MRI showed multiple acute and chronic lacunar infarcts in the pons and bilateral cerebral hemispheres. A previously reported pathogenic mutation of PADMAL, COL4A1 c.*32G > T, was identified and found to be absent in both parents. Identity testing confirmed the biological parentage, classifying the c.*32G > T variant as a de novo mutation. The discovery of PADMAL in a patient with a de novo mutation indicates that COL4A1 gene miR-29-binding site variant sequencing should be considered in patients exhibiting typical clinical and MRI features, even if there is no family history.

This report presents a case of pontine autosomal dominant microangiopathy with leukoencephalopathy (PADMAL) in a 35 year-old male patient. The patient exhibited a consistent history of recurrent ischemic strokes, concentrated primarily in the pons region, accompanied by concurrent manifestations of leukoencephalopathy and microbleeds. Genetic evaluation revealed a heterozygous missense mutation consistent with c.3431C>G, p. Thr1144Arg substitution within exon 40 of the COL4A1 gene. This mutation was also identified in the patient's mother, affirming an autosomal dominant inheritance model. Our findings serve as testament to the potential role of mutation in the exon 40 of COL4A1 in the pathogenesis and progression of PADMAL, contributing to ongoing efforts aimed at better understanding the genetic basis of this debilitating disorder.

(1) Description of clinical and cranial MRI features in the original Pontine Autosomal Dominant Microangiopathy with Leukoencephalopathy (PADMAL) family and correlation with the segregation analysis of the causative collagen 4A1 gene (COL4A1) variant. (2) Sequence analysis of the COL4A1 miRNA-binding site containing the causative variant in two independent cross-sectional samples of sporadic stroke patients. Sanger sequencing of the COL4A1 miRNA-binding site in the PADMAL family and 874 sporadic stroke patients. PADMAL shows adult-onset usually between 30 and 50 years of age with initial brainstem-related symptoms most commonly dysarthria, with progression to dementia and tetraparesis. Radiologically pontine lacunes are followed by supratentorial white matter involvement. Radiological onset may precede clinical symptoms. We found no variants in the COL4A1 miRNA-binding site of sporadic stroke patients. Our results allow an early diagnosis of PADMAL based on cranial MRI, clinical signs, and confirmatory sequencing of the COL4A1 miRNA-29-binding site. COL4A1 miRNA-29-binding site variants do not contribute to a sizeable proportion of sporadic stroke.

Cerebral small vessel disease (cSVD) is a heterogeneous group of disorders. Screening of known cSVD genes identifies the causative mutation in <15% of familial cSVD cases. We sought to identify novel causes of cSVD. We used linkage analysis and exome sequencing to identify the causal mutation in a French cSVD family. The identified candidate gene was then screened in 202 cSVD unrelated probands, including 1 proband from the first reported pontine autosomal dominant microangiopathy with leukoencephalopathy (PADMAL) family. Sanger sequencing was used to confirm variants in all mutated probands and analyze their segregation in probands' relatives. Mutation consequences were assessed with luciferase reporter assays and real-time quantitative polymerase chain reaction (RT-qPCR). A candidate heterozygous variant located in a predicted miR-29 microRNA binding site, within the 3' untranslated region of COL4A1, was identified in the large French cSVD family. Five additional unrelated probands, including the PADMAL proband, harbored heterozygous variants in this microRNA binding site. Variants cosegregated with the affected phenotype, and cumulative logarithm of odds score reached 6.03, establishing linkage to this locus. A highly significant difference was observed when comparing the number of variants within this binding site in cases and controls (p = 1.77 × 10E-12). RT-qPCR analyses of patients' primary fibroblasts and luciferase reporter assays strongly favor an upregulation of COL4A1 mediated by disruption of miR-29 binding to its target site. Magnetic resonance imaging features were characterized by the presence of multiple pontine infarcts in all symptomatic mutation carriers. Mutations upregulating COL4A1 expression lead to PADMAL, a severe early onset ischemic cSVD, distinct from the various phenotypes associated with COL4A1 missense glycine mutations. Ann Neurol 2016;80:741-753.