Partly due to these technological and analytic developments, the search for links between CNVs and disease susceptibility has been actively pursued in recent years. Structural variation has of course long been known to influence such Mendelian disorders as Williams-Beuren syndrome or Charcot-Marie Tooth neuropathy Type 1A, but more recently there has been widespread interest in the study of CNVs as mediators of more common complex diseases. The contribution of structural variation to certain neurodevelopmental disorders such as schizophrenia and autism spectrum disorder has been investigated by recent studies of de novo copy number variation [4]. A common 20 kb deletion upstream of IRGM in perfect linkage disequilibrium (r2 = 1.0) with the SNP most strongly associated with Crohn's disease in the region has recently been shown to alter IRGM regulation, which in turn is known to affect autophagy, consistent with the deletion polymorphism being the causal allele [5]. Similarly, a 45 kb deletion polymorphism in NEGR1 has been shown to be the likely causal variant for the reproducible association with body mass index in humans, demonstrating a neuronal influence on
