Deficiency of MFSD7c results in microcephaly-associated vasculopathy in Fowler syndrome
Pazhanichamy Kalailingam, … , Karin Weiss, Long N. Nguyen
Pazhanichamy Kalailingam, … , Karin Weiss, Long N. Nguyen
Published May 5, 2020
Citation Information: J Clin Invest. 2020;130(8):4081-4093. https://doi.org/10.1172/JCI136727.
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Research Article Vascular biology

Deficiency of MFSD7c results in microcephaly-associated vasculopathy in Fowler syndrome

Abstract

Several missense mutations in the orphan transporter FLVCR2 have been reported in Fowler syndrome. Affected subjects exhibit signs of severe neurological defects. We identified the mouse ortholog Mfsd7c as a gene expressed in the blood-brain barrier. Here, we report the characterizations of Mfsd7c-KO mice and compare these characterizations to phenotypic findings in humans with biallelic FLVCR2 mutations. Global KO of Mfsd7c in mice resulted in late-gestation lethality, likely due to CNS phenotypes. We found that the angiogenic growth of CNS blood vessels in the brain of Mfsd7c-KO embryos was inhibited in cortical ventricular zones and ganglionic eminences. Vascular tips were dilated and fused, resulting in glomeruloid vessels. Nonetheless, CNS blood vessels were intact, without hemorrhage. Both embryos and humans with biallelic FLVCR2 mutations exhibited reduced cerebral cortical layers, enlargement of the cerebral ventricles, and microcephaly. Transcriptomic analysis of Mfsd7cK-KO embryonic brains revealed upregulation of genes involved in glycolysis and angiogenesis. The Mfsd7c-KO brain exhibited hypoxia and neuronal cell death. Our results indicate that MFSD7c is required for the normal growth of CNS blood vessels and that ablation of this gene results in microcephaly-associated vasculopathy in mice and humans.

Authors

Pazhanichamy Kalailingam, Kai Qi Wang, Xiu Ru Toh, Toan Q. Nguyen, Madhuvanthi Chandrakanthan, Zafrul Hasan, Clair Habib, Aharon Schif, Francesca Clementina Radio, Bruno Dallapiccola, Karin Weiss, Long N. Nguyen

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Figure 7

Mfsd7c-KO embryos exhibited severe hypoxia.

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Mfsd7c-KO embryos exhibited severe hypoxia. (A and B) Representative im...
(A and B) Representative images of brain sections of WT (A) and KO (B) embryos were stained with CD31 to visualize blood vessels and the monoclonal antibody to detect hypoxic neuronal cells after injection of pimonidazole to the pregnant mice. Top panels in A and B are images from ventral sides of the WT and KO embryo brains, and the bottom panels are dorsal sides, including thalamus and hindbrain regions. In the ventral images in B, hypoxia was detected in the GE of KO embryos. The hypoxia was also present in the brainstem from these KO sections. (C) Enlarged images from GEs of WT and KO embryos. Experiment was repeated three times. n = 3–4 embryos per genotype. (D) Quantification of hypoxic signals in the GEs and thalamus/midbrain regions. ***P < 0.001, 2-tailed t test. Each dot represents 1 section from 3 WT and 4 KO embryos.