Background Individuals affected with autism often suffer additional co-morbidities such as intellectual disability. The genes contributing to autism cluster on a relatively limited number of cellular pathways, including chromatin remodeling. However, limited information is available on how mutations in single genes can result in such pleiotropic clinical features in affected individuals. In this review, we summarize available information on one of the most frequently mutated genes in syndromic autism the Activity-Dependent Neuroprotective Protein (ADNP). Results Heterozygous and predicted loss-of-function ADNP mutations in individuals inevitably result in the clinical presentation with the Helsmoortel–Van der Aa syndrome, a frequent form of syndromic autism. ADNP, a zinc finger DNA-binding protein has a role in chromatin remodeling: The protein is associated with the pericentromeric protein HP1, the SWI/SNF core complex protein BRG1, and other members of this chromatin remodeling complex and, in murine stem cells, with the chromodomain helicase CHD4 in a ChAHP complex. ADNP has recently been shown to possess R-loop processing activity. In addition, many additional functions, for instance, in association with cytoskeletal proteins have been linked to ADNP. Conclusions We here present an integrated evaluation of all current aspects of gene function and evaluate how abnormalities in chromatin remodeling might relate to the pleiotropic clinical presentation in individual“s” with Helsmoortel–Van der Aa syndrome.

Heterozygous de novo mutations in the Activity-Dependent Neuroprotective Homeobox (ADNP) protein were found to be the common cause underlying the Helsmoortel-Van der Aa syndrome (HVDAS). With most of the patient mutations situated in the last exon, we previously demonstrated the predicted escape from nonsense-mediated decay by detecting mutant ADNP mRNA. In this study wild-type and mutant forms of ADNP are investigated at the protein level and therefore optimal detection of the protein is required. We postulate that detection of ADNP by means of western blotting has been ambiguous and address different strategies to optimize the ADNP signal. Validation of a new N-terminal ADNP antibody (Aviva Systems) using a blocking peptide competition assay allowed to differentiate between specific and non-specific signals in different sample materials, resulting in a unique band signal around 150 kDa for ADNP, above its theoretical molecular weight of 124 kDa. Detection with different C-terminal antibodies confirmed the signals at an observed molecular weight of 150 kDa. By means of both a GFPSpark® and and Flag®-tag N-terminally fused to a human ADNP expression vector, we detected wild-type ADNP together with mutant forms after introduction of patient mutations in E. coli expression systems by site-directed mutagenesis. However, western blot assessment of immortalized lymphoblastoid cell lines and post-mortem patient brain material failed to detect mutant ADNP protein, a scientific paradox up to today not yet resolved. This study aims to shape awareness for critical western blot assessment of ADNP variants and stimulates further research regarding ADNP expression by means of a validated multi-antibody approach.