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Intellectual disability v9.193 LDB1 Arina Puzriakova gene: LDB1 was added
gene: LDB1 was added to Intellectual disability. Sources: Literature
Q4_25_promote_green tags were added to gene: LDB1.
Mode of inheritance for gene: LDB1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Publications for gene: LDB1 were set to 39680505; 38091987; 33077954
Phenotypes for gene: LDB1 were set to Congenital hydrocephalus, MONDO:0016349
Review for gene: LDB1 was set to GREEN
Added comment: - Allington et al. 2024 (PMID: 39680505) investigate a cohort of 2697 trios with congenital primary cerebral ventriculomegaly using WES. Eight unrelated individuals identified with de novo variants in LDB1 (7 LOF, 1 predicted damaging missense) - exhibiting perinatally diagnosed cerebral ventriculomegaly, including neurosurgically treated congenital hydrocephalus. Additionally, 5/8 GDD, 3/8 autism, 2/8 delayed gross motor development, 2/8 had congenital heart defects (inc. coarctation, PDA), 2/8 camptodactyly.

Additional case was identified from GeneMatcher with a de novo frameshift variants in LDB1. Phenotypes include severe ventriculomegaly, absence of well formed gyri, severe limb contractures and camptodactyly. Search of Decipher/DDD also revealed 4 pathogenic de novo variants in LDB1 and associated binding partners in individuals congenital ventriculomegaly.

- Torene et al. 2023 (PMID: 38091987) identified three individuals with protein truncating variants. Two individuals with de novo variants both had ventriculomegaly, hypotonia, GDD, craniofacial abnormalities. The third individual inherited the variants from an asymptomatic mother, and displayed developmental delay, hypotonia, congenital heart defects and a small hypoplastic hippocampi but did not have ventriculomegaly or craniofacial anomalies.

- Jin et al. 2020 (PMID: 33077954) also report an individual with a de novo LOF variant in this gene who had congenital hydrocephalus but details on this case are otherwise limited.
Sources: Literature
Intellectual disability v3.1514 MPI Arina Puzriakova Tag for-review was removed from gene: MPI.
Intellectual disability v3.1510 MPI Sarah Leigh commented on gene: MPI
Intellectual disability v3.1509 MPI Arina Puzriakova Source Expert Review Red was added to MPI.
Rating Changed from Green List (high evidence) to Red List (low evidence)
Intellectual disability v3.1216 CLCN3 Zornitza Stark gene: CLCN3 was added
gene: CLCN3 was added to Intellectual disability. Sources: Literature
Mode of inheritance for gene: CLCN3 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Publications for gene: CLCN3 were set to 34186028
Phenotypes for gene: CLCN3 were set to Neurodevelopmental disorder
Mode of pathogenicity for gene: CLCN3 was set to Other
Review for gene: CLCN3 was set to GREEN
gene: CLCN3 was marked as current diagnostic
Added comment: 11 individuals reported, 9 that carried 8 different rare heterozygous missense variants in CLCN3, and 2 siblings that were homozygous for an NMD-predicted frameshift variant likely abolishing ClC-3 function. All missense variants were confirmed to be de novo in eight individuals for whom parental data was available.

The 11 individuals in the cohort share clinical features of variable severity. All 11 have GDD or ID and dysmorphic features, and a majority has mood or behavioural disorders and structural brain abnormalities:
- Structural brain abnormalities on MRI (9/11) included partial or full agenesis of the corpus callosum (6/9), disorganized cerebellar folia (4/9), delayed myelination (3/9), decreased white matter volume (3/9), pons hypoplasia (3/9), and dysmorphic dentate nuclei (3/9). Six of those with brain abnormalities also presented with seizures.
- Nine have abnormal vision, including strabismus in four and inability to fix or follow in the two with homozygous loss-of-function variants.
- Hypotonia ranging from mild to severe was reported in 7 of the 11 individuals.
- Six have mood or behavioural disorders, particularly anxiety (3/6).
- Consistent dysmorphic facial features included microcephaly, prominent forehead, hypertelorism, down-slanting palpebral fissures, full cheeks, and micrognathia.

The severity of disease in the two siblings with homozygous disruption of ClC-3 is consistent with the drastic phenotype seen in Clcn3 KO mice. The disease was more severe in two siblings carrying homozygous loss-of-function variants with the presence of GDD, absent speech, seizures, and salt and pepper fundal pigmentation in both individuals, with one deceased at 14 months of age. The siblings also had significant neuroanatomical findings including diffusely decreased white matter volume, thin corpora callosa, small hippocampi, and disorganized cerebellar folia. Supporting biallelic inheritance for LoF variants, disruption of mouse Clcn3 results in drastic neurodegeneration with loss of the hippocampus a few months after birth and early retinal degeneration. Clcn3−/− mice display severe neurodegeneration, whereas heterozygous Clcn3+/− mice appear normal.

Patch-clamp studies were used to investigate four of the missense variants. These suggested a gain of function in two variants with increased current in HEK cells, however they also showed reduced rectification of voltage and a loss of transient current, plus decreased current amplitude, glycosylation and surface expression when expressed in oocytes, and were suspected to interfere with channel gating and a negative feedback mechanism. These effects were also shown to vary depending on pH levels. The current of the remaining two variants did not differ from WT. For heterozygous missense variants, the disruption induced may be at least partially conferred to mutant/WT homodimers and mutant/ClC-4 heterodimers.

Both loss and gain of function in this gene resulted in the same phenotype.

Green for mono-allelic variants, Amber/Red for bi-allelic.
Sources: Literature
Intellectual disability v3.688 MPI Arina Puzriakova Publications for gene: MPI were set to 9525984; 3080572; 9585601
Intellectual disability v3.687 MPI Arina Puzriakova Phenotypes for gene: MPI were changed from CONGENITAL DISORDERS OF GLYCOSYLATION to Congenital disorder of glycosylation, type Ib, OMIM:602579; MPI-CDG, MONDO:0011257
Intellectual disability v3.686 MPI Arina Puzriakova reviewed gene: MPI: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: ; Mode of inheritance: None
Intellectual disability v3.686 MPI Arina Puzriakova Tag for-review tag was added to gene: MPI.
Intellectual disability v3.660 MPI Zornitza Stark reviewed gene: MPI: Rating: RED; Mode of pathogenicity: None; Publications: 12414827, 9585601, 10980531, 33098580, 33204592, 32905087, 32266963, 30242110; Phenotypes: Congenital disorder of glycosylation, type Ib, MIM# 602579, MPI-CDG MONDO:0011257; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal
Intellectual disability v3.644 KDM4B Zornitza Stark gene: KDM4B was added
gene: KDM4B was added to Intellectual disability. Sources: Literature
Mode of inheritance for gene: KDM4B was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Publications for gene: KDM4B were set to 33232677
Phenotypes for gene: KDM4B were set to Global developmental delay, intellectual disability and neuroanatomical defects
Review for gene: KDM4B was set to GREEN
Added comment: Nine individuals with mono-allelic de novo or inherited variants in KDM4B.

All individuals presented with dysmorphic features and global developmental delay (GDD) with language and motor skills most affected. Three individuals had a history of seizures, and four had anomalies on brain imaging ranging from agenesis of the corpus callosum with hydrocephalus to cystic formations, abnormal hippocampi, and polymicrogyria.

In a knockout mouse the total brain volume was significantly reduced with decreased
size of the hippocampal dentate gyrus, partial agenesis of the corpus callosum, and ventriculomegaly.
Sources: Literature
Intellectual disability v2.468 MPI Louise Daugherty Source Victorian Clinical Genetics Services was added to MPI.
Intellectual disability MPI BRIDGE consortium edited their review of MPI
Intellectual disability MPI BRIDGE consortium edited their review of MPI
Intellectual disability MPI BRIDGE consortium reviewed MPI