1. Panels
  2. Intellectual disability
  3. TIAM1
Genes in panel
Prev Next
Regions in panel
Prev Next

Intellectual disability

Gene: TIAM1

Green List (high evidence)
TIAM1 (T-cell lymphoma invasion and metastasis 1)
EnsemblGeneIds (GRCh38): ENSG00000156299
EnsemblGeneIds (GRCh37): ENSG00000156299
OMIM: 600687, Gene2Phenotype
TIAM1 is in 2 panels

3 reviews

Arina Puzriakova (Genomics England Curator)

Green List (high evidence)

The rating of this gene has been updated to Green and the mode of inheritance set to 'BIALLELIC, autosomal or pseudoautosomal' following NHS Genomic Medicine Service approval.
Created: 30 Jan 2023, 5:50 p.m. | Last Modified: 30 Jan 2023, 5:50 p.m.
Panel Version: 4.53
Created: 30 Jan 2023, 5:50 p.m.
Last Modified: 30 Jan 2023, 5:50 p.m.
Panel version: 4.53

Sarah Leigh (Genomics England Curator)

Green List (high evidence)

Associated with relevant phenotype in OMIM, but not associated with phenotype in Gen2Phen. PMID: 35240055 reports six TIAM1 variants in four unrelated cases (5 cases in total) of Neurodevelopmental disorder with language delay and seizures, OMIM:619908. All of the cases displayed seizures and intellectual disability, where an assessment was made. The drospohila ortholog (still life) and funtional studies supported this gene disease association (PMID: 35240055).
Created: 25 Aug 2022, 9:29 a.m. | Last Modified: 25 Aug 2022, 9:29 a.m.
Panel Version: 3.1684
Comment on list classification: There is enough evidence for this gene to be rated GREEN at the next major review.
Created: 25 Aug 2022, 9:12 a.m. | Last Modified: 25 Aug 2022, 9:12 a.m.
Panel Version: 3.1683
Created: 25 Aug 2022, 9:12 a.m.
Last Modified: 25 Aug 2022, 9:12 a.m.
Panel version: 3.1684

Konstantinos Varvagiannis (Other)

I don't know

Lu et al (2022 - PMID: 35240055) describe 5 individuals (from 4 families) with biallelic TIAM1 missense variants.

The phenotype overall corresponded to a neurodevelopmental disorder with DD (5/5), ID (4/4 individuals of relevant age - 3 families), speech delay (5/5), seizures (5/5 - onset: 2m-13y) and behavioral abnormalities (2/2, sibs with autism and ADHD). Several subjects had endocrine symptoms, namely hypothyroidism (N=3 - 2 families), Addison's disease (1) or hypomagnesemia (1). Non-consistent abnormalities were reported in (3/3) subjects who had a brain MRI.

Previous investigations were mentioned for 3 individuals (incl. 2 sibs) and included normal CMA and/or metabolic workup.

Singleton or trio exome sequencing (in one family) revealed biallelic missense TIAM1 variants.

6 different missense variants were reported, all ultra-rare or not present in gnomAD (also o/e:0.2, pLI:0.96), with CADD scores in favor of deleterious effect (NM_001353694.2): c.67C>T/p.Arg23Cys*, c.2584C>T/p.Leu862Phe*, c.983G>T/p.Gly328Val*, c.4640C>A/p.Ala1547Glu, c.1144G>C/p.Gly382Arg, c.4016C>T/p.Ala1339Val.

TIAM1 encodes a RAC1-specific guanine exchange factor (GEF), regulating RAC1 signaling pathways that in turn affect cell shape, migration, adhesion, growth, survival, and polarity, and influence actin cytoskeletal organization, endocytosis, and membrane trafficking. RAC1 signaling plays important role in control of neuronal morphogenesis and neurite outgrowth (based on the summary by Entrez and authors).

TIAM1 is highly expressed in human brain (GTEx).

The authors provide evidence that sif, the Drosophila ortholog, is expressed primarily in neurons of the fly CNS (but not in glia). Using different sif LoF mutant flies they demonstrate that loss of sif impairs viability. Surviving flies exhibited climbing defects and seizure-like behaviors, both significantly rescued upon UAS-sif expression. Neuronal specific sif knockdown resulted in similar phenotypes to ubiquitous knockdown, while glial knockdown did not result in climbing defects.

The semi-lethal phenotype could be fully rescued by expression of the fly sif cDNA, but only partially by human TIAM1 cDNA reference. Upon expression, 3 patient-variants (R23C, L862F, G328V) had variable rescue abilities similar to or lower (R23C) than TIAM1 Ref. TIAM1 Ref and variants could not rescue the neurological phenotypes though. Higher/ectopic expression of sif or TIAM1 Ref was toxic, which was also observed to a lesser extent for variants.

Overall, the evidence provided suggests that the 3 variants tested induce partial LoF.

In a recent study cited (PMID: 33328293), Tiam1 KO mice had simplified dendritic arbors, reduced spine density and diminished excitatory transmission in dentate gyrus. The authors comment that this mouse model presented only subtle behavioral abnormalities which they speculate may be secondary to GEF redundancy (eg. Tiam2).

There is no TIAM1-associated phenotype in OMIM/G2P/SysID. TIAM1 is included in PanelApp Australia in the ID and epilepsy panels with green rating.

Consider inclusion in the current panel with amber rating [As authors discuss: some phenotypic features differed in their small cohort and the contribution of other recessive conditions in 2 consanguineous families cannot be excluded. Also: in fig S1 only status of parents but not of affected/unaffected sibs is specified with the exception of Fam1].
Sources: Literature
Created: 13 Mar 2022, 11:49 a.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Delayed speech and language development; Global developmental delay; Intellectual disability; Seizures; Behavioral abnormality; Abnormality of the endocrine system; Hypothyroidism; Abnormality of nervous system morphology

Publications

Created: 13 Mar 2022, 11:49 a.m.

Panel version: 3.1518

Details

Mode of Inheritance
BIALLELIC, autosomal or pseudoautosomal
Sources
  • Expert Review Green
  • NHS GMS
Phenotypes
  • Neurodevelopmental disorder with language delay and seizures, OMIM:619908
OMIM
600687
Clinvar variants
Variants in TIAM1
Penetrance
Complete
Publications
Panels with this gene

History Filter Activity

31 Jan 2023, Gel status: 3

Removed Tag, Removed Tag

Arina Puzriakova (Genomics England Curator)

Tag Q3_22_rating was removed from gene: TIAM1. Tag Q3_22_MOI was removed from gene: TIAM1.

30 Jan 2023, Gel status: 3

Added New Source, Added New Source, Status Update

Arina Puzriakova (Genomics England Curator)

Source NHS GMS was added to TIAM1. Source Expert Review Green was added to TIAM1. Rating Changed from Amber List (moderate evidence) to Green List (high evidence)

25 Aug 2022, Gel status: 2

Added Tag, Added Tag

Sarah Leigh (Genomics England Curator)

Tag Q3_22_rating tag was added to gene: TIAM1. Tag Q3_22_MOI tag was added to gene: TIAM1.

25 Aug 2022, Gel status: 2

Set Phenotypes

Sarah Leigh (Genomics England Curator)

Phenotypes for gene: TIAM1 were changed from Delayed speech and language development; Global developmental delay; Intellectual disability; Seizures; Behavioral abnormality; Abnormality of the endocrine system; Hypothyroidism; Abnormality of nervous system morphology to Neurodevelopmental disorder with language delay and seizures, OMIM:619908

25 Aug 2022, Gel status: 2

Entity classified by Genomics England curator

Sarah Leigh (Genomics England Curator)

Gene: tiam1 has been classified as Amber List (Moderate Evidence).

13 Mar 2022, Gel status: 0

Created, Added New Source, Set mode of inheritance, Set publications, Set Phenotypes, Set penetrance

Konstantinos Varvagiannis (Other)

gene: TIAM1 was added gene: TIAM1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TIAM1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TIAM1 were set to 35240055; 33328293 Phenotypes for gene: TIAM1 were set to Delayed speech and language development; Global developmental delay; Intellectual disability; Seizures; Behavioral abnormality; Abnormality of the endocrine system; Hypothyroidism; Abnormality of nervous system morphology Penetrance for gene: TIAM1 were set to Complete Review for gene: TIAM1 was set to AMBER