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Intellectual disability syndromic and non-syndromic v0.6222 DIAPH1 Bryony Thompson reviewed gene: DIAPH1: Rating: GREEN; Mode of pathogenicity: None; Publications: 39076976, 24781755, 26463574, 33662367; Phenotypes: progressive microcephaly-seizures-cortical blindness-developmental delay syndrome MONDO:0014714; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal; Current diagnostic: yes
Intellectual disability syndromic and non-syndromic v0.6222 DIAPH1 Zornitza Stark Phenotypes for gene: DIAPH1 were changed from to progressive microcephaly-seizures-cortical blindness-developmental delay syndrome MONDO:0014714
Intellectual disability syndromic and non-syndromic v0.6219 DIAPH1 Zornitza Stark reviewed gene: DIAPH1: Rating: GREEN; Mode of pathogenicity: None; Publications: ; Phenotypes: progressive microcephaly-seizures-cortical blindness-developmental delay syndrome MONDO:0014714; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
Intellectual disability syndromic and non-syndromic v0.6215 DIAPH1 Ken Lee Wan changed review comment from: Seizures, cortical blindness, and microcephaly syndrome (SCBMS) is an autosomal recessive neurodevelopmental disorder characterized by microcephaly, early-onset seizures, severely delayed psychomotor development, and cortical blindness. Affected individuals also tend to show poor overall growth with short stature (MIM: 616632).

Biallelic loss-of-function DIAPH1 variants have been reported in 3 Middle Eastern consanguineous families with a unique syndrome of early onset seizures, progressive microcephaly, intellectual disability and severe visual impairment (PMIDs: 24781755; 26463574). Western blot analysis showed lack of the mDia1 protein for affected individuals (PMID: 24781755).; to: Seizures, cortical blindness, and microcephaly syndrome (SCBMS) is an autosomal recessive neurodevelopmental disorder characterized by microcephaly, early-onset seizures, severely delayed psychomotor development and cortical blindness. Affected individuals also tend to show poor overall growth with short stature (MIM: 616632).

Biallelic loss-of-function DIAPH1 variants have been reported in 3 Middle Eastern consanguineous families with a unique syndrome of early onset seizures, progressive microcephaly, intellectual disability and severe visual impairment (PMIDs: 24781755; 26463574). Western blot analysis showed lack of the mDia1 protein for affected individuals (PMID: 24781755).
Intellectual disability syndromic and non-syndromic v0.6207 DIAPH1 Ken Lee Wan reviewed gene: DIAPH1: Rating: AMBER; Mode of pathogenicity: None; Publications: 24781755, 26463574; Phenotypes: progressive microcephaly-seizures-cortical blindness-developmental delay syndrome MONDO:0014714; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal; Current diagnostic: yes
Intellectual disability syndromic and non-syndromic v0.5079 ALMS1 Christa Whelan reviewed gene: ALMS1: Rating: RED; Mode of pathogenicity: None; Publications: MIM # 203800, 27142762, 25846608, 18154657, 25296579, 17146208, 17940554, 22043170, 31889847, 2231654, 8418611, 8181924, 8556827, 9663233, 25864795, 8556827, 11941369.; Phenotypes: Alström Syndrome (multisystemic), characterized by progressive cone-rod dystrophy leading to blindness, sensorineural hearing loss, childhood obesity associated with hyperinsulinemia, and type 2 diabetes mellitus, Dilated cardiomyopathy occurs in approximately 70% of patients during infancy or adolescence, Renal failure, pulmonary, hepatic, and urologic dysfunction are often observed, and systemic fibrosis develops with age MIM# 203800; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
Intellectual disability syndromic and non-syndromic v0.4160 NDN Zornitza Stark Phenotypes for gene: NDN were changed from to Prader-Willi syndrome, MIM# 176270
Intellectual disability syndromic and non-syndromic v0.3127 MPP5 Konstantinos Varvagiannis gene: MPP5 was added
gene: MPP5 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: MPP5 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Publications for gene: MPP5 were set to 33073849
Phenotypes for gene: MPP5 were set to Global developmental delay; Intellectual disability; Delayed speech and language development; Developmental regression; Behavioral abnormality
Penetrance for gene: MPP5 were set to unknown
Review for gene: MPP5 was set to GREEN
Added comment: Sterling et al (2020 - PMID: 33073849) provide information on the phenotype of 3 individuals with de novo MPP5 variants.

Common features included global developmental delay, intellectual disability (3/3 - severe in 2/3), speech delay/regression (the latter in at least 2) and behavioral abnormalities. Variable other features were reported, among others microcephaly (1/3), abnormal vision (1/3 : CVI, retinal dystrophy, nystagmus), brain MRI abnormalities (2/3), late-onset seizures (1/3). These subjects displayed variable and non-specific dysmorphic features.

All were investigated by exome sequencing (previous investigations not mentioned).

One subject was found to harbor a de novo mosaic (5/25 reads) stopgain variant, further confirmed by Sanger sequencing [NM_022474.4:c.1555C>T - p.(Arg519Ter). The specific variant is reported once in gnomAD (1/251338). Two de novo missense variants were identified in the remaining individuals [c.1289A>G - p.Glu430Gly / c.974A>C - p.His325Pro). All variants had in silico predictions in favor of a deleterious effect (CADD score >24).

The authors comment that MPP5 encodes an apical complex protein with asymmetric localization to the apical side of polarized cells. It is expressed in brain, peripheral nervous system and other tissues. MPP5 is a member of the membrane-associated guanylate kinase family of proteins (MAGUK p55 subfamily), determining cell polarity at tight junctions.

Previous animal models suggest that complete Mpp5(Pals1) KO in mice leads to near absence of cerebral cortical neurons. Htz KO display reduction in size of cerebral cortex and hippocampus. The gene is expressed in proliferating cell populations of cerebellum and important for establishment cerebellar architecture. Conditional KO of Mpp5(Pals1) in retinal progenitor cells mimics the retinal pathology observed in LCA. [Several refs. provided]

The authors studied a heterozygous CNS-specific Mpp5 KO mouse model. These mice presented microcephaly, decreased cerebellar volume and cortical thickness, decreased ependymal cells and Mpp5 at the apical surface of cortical vertrical zone. The proportion of cortical cells undergoing apoptotic cell death was increased. Mice displayed behavioral abnormalities (hyperactivity) and visual deficits, with ERG traces further suggesting retinal blindness.

Overall the mouse model was thought to recapitulate the behavioral abnormalities observed in affected subjects as well as individual rare features such as microcephaly and abnormal vision.

Haploinsufficiency (rather than a dominant negative effect) is favored as the underlying disease mechanism. This is also in line with a dose dependent effect observed in mice.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.2525 CACNB4 Bryony Thompson gene: CACNB4 was added
gene: CACNB4 was added to Intellectual disability syndromic and non-syndromic. Sources: Literature
Mode of inheritance for gene: CACNB4 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: CACNB4 were set to 32176688
Phenotypes for gene: CACNB4 were set to intellectual disability; psychomotor retardation; blindness; epilepsy; movement disorder; cerebellar atrophy
Review for gene: CACNB4 was set to AMBER
Added comment: A homozygous missense variant (Leu126Pro) was identified in two siblings with intellectual disability, psychomotor retardation, blindness, epilepsy, movement disorder and cerebellar atrophy. In vitro functional assays of the variant identify three potential pathomechanisms: impairs the formation of synaptic P/Q-type calcium channel complexes; prevents activity-dependent nuclear targeting and thus β4-dependent nuclear functions; disturbs complex formation between β4b and the TRAF2 and NCK interacting kinase TNIK.
Sources: Literature
Intellectual disability syndromic and non-syndromic v0.818 NDN Zornitza Stark Marked gene: NDN as ready
Intellectual disability syndromic and non-syndromic v0.818 NDN Zornitza Stark Gene: ndn has been classified as Red List (Low Evidence).
Intellectual disability syndromic and non-syndromic v0.818 NDN Zornitza Stark Classified gene: NDN as Red List (low evidence)
Intellectual disability syndromic and non-syndromic v0.818 NDN Zornitza Stark Gene: ndn has been classified as Red List (Low Evidence).
Intellectual disability syndromic and non-syndromic v0.817 NDN Zornitza Stark reviewed gene: NDN: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: ; Mode of inheritance: None
Intellectual disability syndromic and non-syndromic v0.0 NDN Zornitza Stark gene: NDN was added
gene: NDN was added to Intellectual disability, syndromic and non-syndromic_GHQ. Sources: Expert Review Green,Genetic Health Queensland
Mode of inheritance for gene: NDN was set to Unknown