Variants in CAMTA1

Inspired by a patient's sister

Jacobs EZ, Brown K, Byler MC, D'haenens E, Dheedene A, Henderson LB, Humberson JB, van Jaarsveld RH, Kanani F, Lebel RR, Millan F, Oegema R, Oostra A, Parker MJ, Rhodes L, Saenz M, Seaver LH, Si Y, Vanlander A, Vergult S, Callewaert B. Expanding the molecular spectrum and the neurological phenotype related to CAMTA1 variants. Clin Genet. 2021 Feb;99(2):259-268. doi: 10.1111/cge.13874. Epub 2020 Nov 23. PMID: 33131045.

Abstract

The CAMTA1-associated phenotype was initially defined in patients with intragenic deletions and duplications who showed nonprogressive congenital ataxia, with or without intellectual disability. Here, we describe 10 individuals with CAMTA1 variants: nine previously unreported (likely) pathogenic variants comprising one missense, four frameshift and four nonsense variants, and one missense variant of unknown significance. Six patients were diagnosed following whole exome sequencing and four individuals with exome-based targeted panel analysis. Most of them present with developmental delay, manifesting in speech and motor delay. Other frequent findings are hypotonia, cognitive impairment, cerebellar dysfunction, oculomotor abnormalities, and behavioral problems. Feeding problems occur more frequently than previously observed. In addition, we present a systematic review of 19 previously published individuals with causal variants, including copy number, truncating, and missense variants. We note a tendency of more severe cognitive impairment and recurrent dysmorphic features in individuals with a copy number variant. Pathogenic variants are predominantly observed in and near the N- and C- terminal functional domains. Clinical heterogeneity is observed, but 3'-terminal variants seem to associate with less pronounced cerebellar dysfunction.

Wijnen IGM, Veenstra-Knol HE, Vansenne F, Gerkes EH, de Koning T, Vos YJ, Tijssen MAJ, Sival D, Darin N, Vanhoutte EK, Oosterloo M, Pennings M, van de Warrenburg BP, Kamsteeg EJ. De novo variants in CAMTA1 cause a syndrome variably associated with spasticity, ataxia, and intellectual disability. Eur J Hum Genet. 2020 Jun;28(6):763-769. doi: 10.1038/s41431-020-0600-5. Epub 2020 Mar 10. PMID: 32157189; PMCID: PMC7253440.

Abstract

Previously, intragenic CAMTA1 copy number variants (CNVs) have been shown to cause non-progressive, congenital ataxia with or without intellectual disability (OMIM#614756). However, ataxia, intellectual disability, and dysmorphic features were all incompletely penetrant, even within families. Here, we describe four patients with de novo nonsense, frameshift or missense CAMTA1 variants. All four patients predominantly manifested features of ataxia and/or spasticity. Borderline intellectual disability and dysmorphic features were both present in one patient only, and other neurological and behavioural symptoms were variably present. Neurodevelopmental delay was found to be mild. Our findings indicate that also nonsense, frameshift and missense variants in CAMTA1 can cause a spastic ataxia syndrome as the main phenotype.

Thevenon J, Lopez E, Keren B, Heron D, Mignot C, Altuzarra C, Béri-Dexheimer M, Bonnet C, Magnin E, Burglen L, Minot D, Vigneron J, Morle S, Anheim M, Charles P, Brice A, Gallagher L, Amiel J, Haffen E, Mach C, Depienne C, Doummar D, Bonnet M, Duplomb L, Carmignac V, Callier P, Marle N, Mosca-Boidron AL, Roze V, Aral B, Razavi F, Jonveaux P, Faivre L, Thauvin-Robinet C. Intragenic CAMTA1 rearrangements cause non-progressive congenital ataxia with or without intellectual disability. J Med Genet. 2012 Jun;49(6):400-8. doi: 10.1136/jmedgenet-2012-100856. PMID: 22693284.

Abstract

Background: Non-progressive congenital ataxias (NPCA) with or without intellectual disability (ID) are clinically and genetically heterogeneous conditions. As a consequence, the identification of the genes responsible for these phenotypes remained limited.

Objective: Identification of a new gene responsible for NPCA and ID. Methods Following the discovery of three familial or sporadic cases with an intragenic calmodulin-binding transcription activator 1 (CAMTA1) rearrangement identified by an array-CGH and recruited from a national collaboration, the authors defined the clinical and molecular characteristics of such rearrangements, and searched for patients with point mutations by direct sequencing.

Results: Intragenic copy number variations of CAMTA1 were all located in the CG-1 domain of the gene. It segregated with autosomal dominant ID with non-progressive congenital cerebellar ataxia (NPCA) in two unrelated families, and was de novo deletion located in the same domain in a child presenting with NPCA. In the patients with ID, the deletion led to a frameshift, producing a truncated protein, while this was not the case for the patient with isolated childhood ataxia. Brain MRI of the patients revealed a pattern of progressive atrophy of cerebellum medium lobes and superior vermis, parietal lobes and hippocampi. DNA sequencing of the CG-1 domain in 197 patients with sporadic or familial non-syndromic intellectual deficiency, extended to full DNA sequencing in 50 patients with ID and 47 additional patients with childhood ataxia, identified no pathogenic mutation.

Magnin E, Blagosklonov O, Sylvestre G, Minot D, Thevenon J, Faivre L, Boulahdour H, Thauvin-Robinet C, Rumbach L. Neuropsychological and neuroimaging phenotype induced by a CAMTA1 mutation. Brain Dev. 2014 Sep;36(8):711-5. doi: 10.1016/j.braindev.2013.09.008. Epub 2013 Oct 18. PMID: 24145135.

Abstract

Background/aims: CAMTA1 mutations have recently been reported in families with intellectual disability and/or non-progressive congenital ataxias. The objective of this study was to describe the neuropsychological and neuroimaging phenotype of CAMTA1 mutation.

Methods: We performed neuropsychological examinations, MRI and FDG-PET imaging in three patients with autosomal dominant mild intellectual disabilities and ataxia induced by a CAMTA1 intragenic deletion at 1p36.31p36.23.

Results: Neuropsychological tests showed similar findings in two patients, with low information processing speed, slow memory consolidation, phonological disorders, working memory deficits, but mainly preserved executive function. Bilateral parietal and medial temporal abnormalities were found on brain MRI. Diffuse parieto-occipital and local left temporo-parietal decrease of FDG uptake was observed on PET images.

Conclusion: These results suggest that CAMTA1 mutation may induce an unusual neuropsychological profile and parieto-temporal developmental abnormalities. We recommend screening for CAMTA1 mutations in patients with autosomal dominant mild intellectual disability presenting with similar a phenotype.

Conclusion: The authors have evidence that loss-of-function of CAMTA1, a brain-specific calcium responsive transcription factor, is responsible for NPCA with or without ID. Accession numbers CAMTA1 reference sequence used was ENST00000303635. Protein sequence was ENSP00000306522.