Background and Purpose:
Cerebral cavernous malformation (CCM) is a common cerebrovascular disease. CCMs are major causes of stroke, cerebral hemorrhage, and neurological deficits in young individuals. Loss-of-function mutations in
CCM1
,
CCM2
, and
CCM3
have been identified to cause CCM in humans.
Ccm2-like
(
Ccm2l
) is a paralog of
Ccm2
and is predominantly expressed in endothelial cells (ECs). CCM2L (CCM2-like) competes with CCM2 for binding to CCM1 and has been shown to have an antagonistic function to that of CCM2 during vascular development. The role of CCM2L in CCM pathogenesis is unknown.
Methods:
We isolated brain ECs from the inducible-CCM mouse models for gene expression analysis. Micro-computed tomography imaging was used to analyze CCM lesion burden from the genetic cross of
Ccm2l
knockout mice (
Ccm2l
−/−
) with
Ccm1
or
Ccm2
-deficient mice to determine the role of
Ccm2l
in CCM pathogenesis. Genetic crosses with
Map3k3
fl/fl
mice were used to determine the role of
Map3k3
in
Ccm2l
-facilitated CCM formation.
Results:
We demonstrated increased
Ccm2l
expression in brain ECs of
Ccm2
-deficient mice. Analysis of RNA-seq data from CCM patient samples revealed a trend of increased
CCM2L
expression and its positive correlation with Kruppel-like factor 2/4
(KLF2/4
) expression. Micro-computed tomography revealed that the deletion of
Ccm2l
in
Ccm2
-deficient mice increased CCM lesion volume compared with that of controls but had no effect on lesion numbers. Correlating to the increased lesion burden,
Klf2/4
mRNA expressions in brain ECs were significantly increased in double knockouts (
Ccm2
- and
Ccm2l
-deficient mice) compared with that of controls (
Ccm2
deficient). Hemizygous deletion of
Map3k3
in ECs relieved CCM lesion burden in the double knockouts. These results suggest that CCM2L regulates the Map3k3-KLF signaling pathway in CCM pathogenesis.
Conclusions:
Loss of CCM2L aggravates CCM lesion formation in the
Ccm2
-deficient mouse model through increased Map3k3-KLF signaling. Our data suggest that increased
Ccm2l
expression is a compensatory mechanism in CCM pathogenesis.
Crystal Structure of CCM3, a Cerebral Cavernous Malformation Protein Critical for Vascular Integrity
