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Intellectual disability v9.224 LSM1 Achchuthan Shanmugasundram Classified gene: LSM1 as Amber List (moderate evidence)
Intellectual disability v9.224 LSM1 Achchuthan Shanmugasundram Added comment: Comment on list classification: There are six unrelated families reported with biallelic LSM 1 variants (c.231+4A>C in five families and p.Asn40Tyr in one family) and with FICUS syndrome (which includes global developmental delay/ intellectual disability). Hence, this gene can be promoted to green rating in the next GMS update.
Intellectual disability v9.224 LSM1 Achchuthan Shanmugasundram Gene: lsm1 has been classified as Amber List (Moderate Evidence).
Intellectual disability v9.223 LSM1 Achchuthan Shanmugasundram Tag Q1_26_promote_green tag was added to gene: LSM1.
Intellectual disability v9.223 LSM1 Achchuthan Shanmugasundram gene: LSM1 was added
gene: LSM1 was added to Intellectual disability. Sources: Literature
Mode of inheritance for gene: LSM1 was set to BIALLELIC, autosomal or pseudoautosomal
Publications for gene: LSM1 were set to 31010896; 36100156; 40204357
Phenotypes for gene: LSM1 were set to FICUS syndrome, OMIM:621193; FICUS syndrome, MONDO:0978296
Review for gene: LSM1 was set to GREEN
Added comment: PMID:31010896 (2019) reported two siblings with global developmental delay, and multiple congenital anomalies affecting the cardiac, genitourinary, and skeletal systems, and abnormal eye movements. They were identified with a homozygous non-canonical splice variant in LSM1 gene (c.231+4A>C) through whole-genome sequencing. There is also functional evidence available from expression studies and mouse model. Lsm1 knockout mice had a partially overlapping phenotype that affected the brain, heart, and eye.

PMID:36100156 (2022) reported the identification of a homozygous missense variant (p.Asn40Tyr) in LSM1 gene via whole-exome in two similarly affected siblings with global neurodevelopmental delay and intellectual disability.

PMID:40204357 (2025) reported six paediatric patients from four unrelated families with homozygous c.231+4A>C variant. They presented with dysmorphic facial features, global developmental delay/ intellectual disability and multisystemic involvement, including urological, cardiac and skeletal manifestations. This variant was identified in Muslim Arab and Ashkenazi Jewish populations and determined as representing a hotspot variant through haplotype analysis. RT-qPCR functional validation demonstrated exon 3 skipping and elevated mutant isoform. The variant was classified as 'Pathogenic' according to the ACMG classification.

This gene has been associated with relevant phenotypes in OMIM (MIM #621193, OMIM record last accessed 06 January 2026), but not yet in Gene2Phenotype.
Sources: Literature
Intellectual disability v2.1015 DDX6 Konstantinos Varvagiannis gene: DDX6 was added
gene: DDX6 was added to Intellectual disability. Sources: Literature
Mode of inheritance for gene: DDX6 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Publications for gene: DDX6 were set to 31422817
Phenotypes for gene: DDX6 were set to Generalized hypotonia; Global developmental delay; Intellectual disability; Unsteady gait; Abnormality of the cardiovascular system; Abnormality of the genitourinary system; Abnormality of limbs
Penetrance for gene: DDX6 were set to unknown
Review for gene: DDX6 was set to GREEN
Added comment: Balak et al. (2019 - PMID: 31422817) report on 5 individuals with de novo likely pathogenic DDX6 variants.

Clinical details are provided for 4. Frequent features included hypotonia, DD, ID (4/4), gait instability, cardiac, genitourinary as well anomalies of the extremities.

DDX6 belongs to the DEAD box family of RNA helicases. This helicase is an essential component of processing bodies (P-bodies / PBs), which are mebrane-less organelles involved in storage of mRNAs and proteins related to mRNA decay thus playing an important role in translational repression/post-transcriptional regulation (PMID: 29381060).

All 5 variants had occurred as de novo events, clustered in exon 11 (NM_004397.5) and affected residues 372-373 of the QxxR motif (c.1115A>G or p.His372Arg / c.1118G>A or p.Arg373Gln) or 390-391 of the V motif (c.1168T>C or p.Cys390Arg / c.1171A>C or p.Thr391Pro / c.1172C>T or p.Thr391Ile). The specific motifs (and RecA-2 domain) are involved in RNA binding, helicase activity and protein-partner binding.

Fibroblasts from 2 individuals were studied. Patient cells contained fewer PBs compared to cells from relatives/control-subjects, despite similar amounts of DDX6 protein upon immunobloting. Additional studies suggested that DDX6 variants caused impaired binding of other DDX6 protein partners involved in PB formation / translation repression (eg. LSM14A, 4E-T, etc) thus resulting in defective PB assembly.

Transcriptome analysis in fibroblasts from one affected individual revealed (significant) differential expression of >1000 genes, enriched for genes related to protein translation, ribosome and RNA processing.

As the authors discuss, given the residual PB assembly, haploinsufficiency is favored over a dominant-negative effect which would result in complete suppression of PBs (as sugested by a previous study of a dominant-negative DDX6 variant - PMID cited: 19297524). [In gnomAD, DDX6 has a Z-score for missense variants of 3.78 and a pLI of 1].

DDX6 is not associated with any phenotype in OMIM.
In G2P it is associated with ID (disease confidence : probable / mutations : all missense/in frame).

As a result, this gene can be considered for inclusion in the ID panel as green (sufficient cases, relevant phenotype, functional studies) or amber.
Sources: Literature