Genes related to autistic traits and empathy

Empathy is the glue that binds human society together. It is the ability to understand one's own and others' mental states and to respond to these appropriately (Baron-Cohen & Wheelwright, 2004). It is of particular interest to study empathy in relation to Autism Spectrum Conditions (ASC), since these are marked by atypical social behaviour. Recent years have seen significant advances in understanding the neurobiology of empathy and its individual differences (Chakrabarti & Baron- Cohen, 2006; Singer & Lamm, 2009). Independently, human molecular genetics has made enormous advances in the past decade, both in delineating the role of specific genes as well as making it possible to identify a large number of sequence variations (polymorphisms) in the whole human genome at once. It is therefore timely to take a multilevel perspective in the study of empathy and social cognition, encompassing all stages from genes to cognition. In this chapter, we provide a brief overview of genetic studies of empathy and other trait measures of ASC. We then describe a recent study from our group, using dimensional phenotypic measures of empathy and autistic traits. Finally, we discuss some initial studies that relate genetic variation to 'intermediate phenotypes' (also known as endophenotypes) relevant to ASC.ASC entail a disability in social and communication development, alongside unusually narrow interests (‘obsessions’) and repetitive behaviour (APA, 1987; ICD-10, 1994). ASC have a genetic basis, indicated by signficantly higher concordance rates in MZ than in DZ twins, and with heritability estimates of over 90% (Bailey et al., 1995; Folstein & Rutter, 1977). Over the last three decades, a number of strategies have been used to discover genes related to ASC. A common feature in most of these studies has been the use of clinical diagnosis of ASC as a categorical phenotype. In these studies, people with a diagnosis of ASC are compared with a group of people without a clinical diagnosis, matched on a variety of measures. This approach has implicated multiple genes, along with environmental (Wagner, Reuhl, Cheh, McRae, & Halladay, 2006) and epigenetic factors (Crespi & Badcock, 2008; Nagarajan et al., 2008). Mixed evidence from genome-wide linkage studies of samples that do not differentiate between classic (low-functioning) autism and Asperger