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Intellectual disability - microarray and sequencing v3.1519 MAP1B Ivone Leong Tag Q3_21_rating was removed from gene: MAP1B.
Intellectual disability - microarray and sequencing v3.1519 MAP1B Sarah Leigh commented on gene: MAP1B
Intellectual disability - microarray and sequencing v3.1519 MAP1B Ivone Leong Source Expert Review Green was added to MAP1B.
Rating Changed from Amber List (moderate evidence) to Green List (high evidence)
Intellectual disability - microarray and sequencing v3.1249 MAP1B Arina Puzriakova Tag Q3_21_rating tag was added to gene: MAP1B.
Intellectual disability - microarray and sequencing v3.1249 MAP1B Arina Puzriakova edited their review of gene: MAP1B: Added comment: MAP1B was flagged by a GLH following identification of some potential cases relating to variants in this gene and predominantly ID phenotypes within 100K data. Although these are pending confirmations (will request update once cases are validated), upon reassessment of MAP1B it was highlighted that inclusion on this panels may still be warranted to increase the likelihood of detecting cases, particularly given that DD/ID is more likely to be observed earlier in the course of disease albeit at varying severities.

For this reason, MAP1B should be promoted to Green status at the next GMS panel review (tagged Q3_21_rating); Changed rating: GREEN
Intellectual disability - microarray and sequencing v3.513 MAP1B Arina Puzriakova Deleted their comment
Intellectual disability - microarray and sequencing v3.513 MAP1B Arina Puzriakova Classified gene: MAP1B as Amber List (moderate evidence)
Intellectual disability - microarray and sequencing v3.513 MAP1B Arina Puzriakova Added comment: Comment on list classification: Maintaining Amber rating as although cognitive impairment is reported in multiple (but not all) cases, often this is mild and not sufficient for a clinical diagnosis of ID. Affected individuals are more likely to be assessed in view of the brain malformations - MAP1B will be added to the 'Malformations of cortical development' panel.
Intellectual disability - microarray and sequencing v3.513 MAP1B Arina Puzriakova Gene: map1b has been classified as Amber List (Moderate Evidence).
Intellectual disability - microarray and sequencing v3.512 MAP1B Arina Puzriakova Phenotypes for gene: MAP1B were changed from Intellectual disability; No OMIM number to Periventricular nodular heterotopia 9, 618918
Intellectual disability - microarray and sequencing v3.511 MAP1B Arina Puzriakova Publications for gene: MAP1B were set to 30150678; 29738522
Intellectual disability - microarray and sequencing v3.510 MAP1B Arina Puzriakova commented on gene: MAP1B: Only one homozygous case identified in a screening study of a congenital microcephaly cohort. Other features included hypochromic microcytic anaemia, lymphocytic colitis, retinal coloboma, dysmorphic features, and normal brain MRI. As this is only considered a candidate variant and the phenotype is not compatible with other monoallelic reports, the evidence is currently insufficient for a disease association with biallelic variants (PMID:30214071)
Intellectual disability - microarray and sequencing v3.510 MAP1B Arina Puzriakova reviewed gene: MAP1B: Rating: AMBER; Mode of pathogenicity: None; Publications: 30150678, 29738522, 30214071, 31317654; Phenotypes: Periventricular nodular heterotopia 9, 618918; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Intellectual disability - microarray and sequencing v3.3 MAP1B Zornitza Stark reviewed gene: MAP1B: Rating: GREEN; Mode of pathogenicity: None; Publications: 31317654, 30150678, 30214071; Phenotypes: Intellectual disability, seizures, PVNH, dysmorphic features; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted; Current diagnostic: yes
Intellectual disability - microarray and sequencing v2.665 MAP1B Ivone Leong Classified gene: MAP1B as Amber List (moderate evidence)
Intellectual disability - microarray and sequencing v2.665 MAP1B Ivone Leong Added comment: Comment on list classification: MAP1B has been given an amber gene rating based on the evidence provided by the expert review. It is not associated with any phenotype on OMIM or Gene2Phenotype.
Intellectual disability - microarray and sequencing v2.665 MAP1B Ivone Leong Gene: map1b has been classified as Amber List (Moderate Evidence).
Intellectual disability - microarray and sequencing v2.664 MAP1B Ivone Leong Phenotypes for gene: MAP1B were changed from Intellectual disability to Intellectual disability; No OMIM number
Intellectual disability - microarray and sequencing v2.510 MAP1B Konstantinos Varvagiannis gene: MAP1B was added
gene: MAP1B was added to Intellectual disability. Sources: Literature,Expert Review
Mode of inheritance for gene: MAP1B was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Publications for gene: MAP1B were set to 30150678; 29738522
Phenotypes for gene: MAP1B were set to Intellectual disability
Penetrance for gene: MAP1B were set to unknown
Review for gene: MAP1B was set to AMBER
Added comment: In PMID 30150678 the authors report on a family with 5 individuals diagnosed with intellectual disability (ID, IQ <= 70 and associated impairments in adaptive function) and 3 further relatives with IQ below 70, not fulfilling the criteria for a clinical diagnosis of ID. A frameshift variant in MAP1B segregated with the ID/low IQ phenotype. This variant was not found in 31463 Icelanders for whom whole genome sequencing data were available.

The authors confirmed association of MAP1B loss-of-function (LoF) variants by demonstrating the presence of 2 other stopgain mutations in 2 further families. Among the 6 mutation carriers in these families, the average IQ was 81 with 2 of these subjects fulfilling the criteria for intellectual disability. 3 of the 6 mutation carriers had a diagnosis of autism spectrum disorder. Carriers demonstrated 24% less white matter volume (-2.1 SD) and 47% less corpus callosum volume (-2.4 SD) compared to controls.

Mean full-scale IQ, performance IQ and verbal IQ were 68.3 (with a SD of 10.5), 66.4 (SD of 9.3) and 74.5 (SD of 14.8) in MAP1B LoF carriers.

All 3 LoF variants reported result in a truncated but stable MAP1B protein as demonstrated by western blot analysis.

MAP1B undergoes post-translational modification and is cleaved (at position 2206) into a heavy chain and a light chain. The authors note that all LoF variants lead to truncation prior to the cleavage site.

As commented by the authors, LoF variants are found in publicly available databases at a frequency of approx. 1 in 10000.

One individual with de novo frameshift variant in Decipher ( https://decipher.sanger.ac.uk/search?q=gene%3AMAP1B#research-variants/results ).

De novo and inherited MAP1B variants have previously been described in individuals with periventricular nodular heterotopia (PMID: 29738522). This was also a feature in 9 individuals in the previous ID study.

Although PMID 30150678 is entitled "MAP1B mutations cause intellectual disability and extensive white matter deficit", intellectual disability was not a feature in all individuals or was rather mild when present.
Sources: Literature, Expert Review