AUTS2 mutations

Inspired by a patient

Beunders G, van de Kamp J, Vasudevan P, Morton J, Smets K, Kleefstra T, de Munnik SA, Schuurs-Hoeijmakers J, Ceulemans B, Zollino M, Hoffjan S, Wieczorek S, So J, Mercer L, Walker T, Velsher L; DDD study, Parker MJ, Magee AC, Elffers B, Kooy RF, Yntema HG, Meijers-Heijboer EJ, Sistermans EA. A detailed clinical analysis of 13 patients with AUTS2 syndrome further delineates the phenotypic spectrum and underscores the behavioural phenotype. J Med Genet. 2016

Aug;53(8):523-32.

Abstract

BACKGROUND:

AUTS2 syndrome is an 'intellectual disability (ID) syndrome' caused by genomic rearrangements, deletions, intragenic duplications or mutations disrupting AUTS2. So far, 50 patients with AUTS2 syndrome have been described, but clinical data are limited and almost all cases involved young children.

METHODS:

We present a detailed clinical description of 13 patients (including six adults) with AUTS2 syndrome who have a pathogenic mutation or deletion in AUTS2. All patients were systematically evaluated by the same clinical geneticist.

RESULTS:

All patients have borderline to severe ID/developmental delay, 83-100% have microcephaly and feeding difficulties. Congenital malformations are rare, but mild heart defects, contractures and genital malformations do occur. There are no major health issues in the adults; the oldest of whom is now 59 years of age. Behaviour is marked by it is a friendly outgoing social interaction. Specific features of autism (like obsessive behaviour) are seen frequently (83%), but classical autism was not diagnosed in any. A mild clinical phenotype is associated with a small in-frame 5' deletions, which are often inherited. Deletions and other mutations causing haploinsufficiency of the full-length AUTS2 transcript give a more severe phenotype and occur de novo.

CONCLUSIONS:

The 13 patients with AUTS2 syndrome with unique pathogenic deletions scattered around the AUTS2 locus confirm a phenotype-genotype correlation. Despite individual variations, AUTS2 syndrome emerges as a specific ID syndrome with microcephaly, feeding difficulties, dysmorphic features and a specific behavioural phenotype.

Beunders G, Voorhoeve E, Golzio C, Pardo LM, Rosenfeld JA, Talkowski ME, Simonic I, Lionel AC, Vergult S, Pyatt RE, van de Kamp J, Nieuwint A, Weiss MM, Rizzu P, Verwer LE, van Spaendonk RM, Shen Y, Wu BL, Yu T, Yu Y, Chiang C, Gusella JF, Lindgren AM, Morton CC, van Binsbergen E, Bulk S, van Rossem E, Vanakker O, Armstrong R, Park SM, Greenhalgh L, Maye U, Neill NJ, Abbott KM, Sell S, Ladda R, Farber DM, Bader PI, Cushing T, Drautz JM, Konczal L, Nash P, de Los Reyes E, Carter MT, Hopkins E, Marshall CR, Osborne LR, Gripp KW, Thrush DL,

Hashimoto S, Gastier-Foster JM, Astbury C, Ylstra B, Meijers-Heijboer H, Posthuma D, Menten B, Mortier G, Scherer SW, Eichler EE, Girirajan S, Katsanis N, Groffen AJ, Sistermans EA. Exonic deletions in AUTS2 cause a syndromic form of intellectual disability and suggest a critical role for the C terminus. Am J Hum Genet. 2013 Feb 7;92(2):210-20.

Abstract

Genomic rearrangements involving AUTS2 (7q11.22) are associated with autism and intellectual disability (ID), although evidence for causality is limited. By combining the results of diagnostic testing of 49,684 individuals, we identified 24 microdeletions that affect at least one exon of AUTS2, as well as one translocation and one inversion each with a breakpoint within the AUTS2 locus. Comparison of 17 well-characterized individuals enabled identification of a variable syndromic phenotype including ID, autism, short stature, microcephaly, cerebral palsy, and facial dysmorphisms. The dysmorphic features were more pronounced in persons with 3'AUTS2 deletions. This part of the gene is shown to encode a C-terminal isoform (with an alternative transcription start site) expressed in the human brain. Consistent with our genetic data, suppression of auts2 in zebrafish embryos caused microcephaly that could be rescued by either the full-length or the C-terminal isoform of AUTS2. Our observations demonstrate a causal role of AUTS2 in neurocognitive disorders, establish a hitherto unappreciated syndromic phenotype at this locus, and show how transcriptional complexity can underpin human pathology. The zebrafish model provides a valuable tool for investigating the etiology of AUTS2 syndrome and facilitating gene-function analysis in the future.

Monderer-Rothkoff G, Tal N, Risman M, Shani O, Nissim-Rafinia M, Malki-Feldman L, Medvedeva V, Groszer M, Meshorer E, Shifman S. AUTS2 isoforms control neuronal differentiation. Mol Psychiatry. 2019 Apr 5. doi: 10.1038/s41380-019-0409-1. [Epub ahead of print]

Abstract

Mutations in AUTS2 are associated with autism, intellectual disability, and microcephaly. AUTS2 is expressed in the brain and interacts with polycomb proteins, yet it is still unclear how mutations in AUTS2 lead to neurodevelopmental phenotypes. Here we report that when neuronal differentiation is initiated, there is a shift in expression from a long isoform to a short AUTS2 isoform. Yeast two-hybrid screen identified the splicing factor SF3B1 as an interactor of both isoforms, whereas the polycomb group proteins, PCGF3 and PCGF5, were found to interact exclusively with the long AUTS2 isoform. Reporter assays showed that the first exons of the long AUTS2 isoform function as a transcription repressor, but the part that consist of the short isoform acts as a transcriptional activator, both influenced by the cellular context. The expression levels of PCGF3 influenced the ability of the long AUTS2 isoform to activate or repress transcription. Mouse embryonic stem cells (mESCs) with heterozygote mutations in Auts2 had an increase in cell death during in vitro corticogenesis, which was significantly rescued by overexpressing the human AUTS2 transcripts. mESCs with a truncated AUTS2 protein (missing exons 12-20) showed premature neuronal differentiation, whereas cells overexpressing AUTS2, especially the long transcript, showed increase in expression of pluripotency markers and delayed differentiation. Taken together, our data suggest that the precise expression of AUTS2 isoforms is essential for regulating transcription and the timing of neuronal differentiation.