Table 1. Classification of cerebral malformations according to cell type origins and morphogenic defects.

Cerebral malformations have been classified into three main groups, according to their cellular origin (Barkovich et al, 2012). Each group has been further subdivided into sub-groups based on distinct morphogenic defects. The principal genes involved in each disorder are reported (Barkovich et al., 2012; Mirzaa et al., 2014). Several genes, such as LIS1, MCPH2 (WDR62), RELN, are involved in more than one morphogenic defect, due to their pleiotropic functions.

Cell type	Cellular function	Classification	Morphogenic defects	Genes
Neural progenitors	Decreased proliferation Increased apoptosis Increased proliferation Decreased apoptosis	GROUP I	I.A and III.D : Microcephalies I.B : Megalocephalies	MCPH1-12, LIS1, NDE1, TBR2 FGFR3, PTEN, GLI3, PTCH1
Neurons	Abnormal migration	GROUP II	II.A : Heterotopia II.B : Lissencephalies II.C : Subcortical heterotopia sublobar dysplasia II.D : Cobblestone malformations	FLNA, RELN LIS1, TUB1A, TUBB2B, TUBB3, CDK5, DYNC1H1, WDR62, RELN DCX, LIS1, NDEL1, TUBA1, TUBB2, ACTG1, ACTB,TUBG1, KIF2A, DYNC1H1 GPR56, FKTN
Heterogenous origins	Abnormal postmigrational development	GROUP III	III.A: Polymicrogyria Schizencephaly III.C : Focal cortical dysplasias III.D : Postmigrational microcephaly	TBR2, PAX6, NDE1, EMX2 PTEN CASK, FOXG1, TCF4