Editing Pleiotropy (section)

==== Autism and schizophrenia ====
{{Main|Autism|Schizophrenia}}
Pleiotropy in genes has been linked between certain [[Mental disorder|psychiatric disorders]] as well. Deletion in the [[22q11.2]] region of [[Chromosome 22 (human)|chromosome 22]] has been associated with [[schizophrenia]] and [[autism]].<ref name=":0">{{cite journal |last1=Vorstman |first1=Jacob A.S. |last2=Breetvelt |first2=Elemi J. |last3=Thode |first3=Kirstin I. |last4=Chow |first4=Eva W.C. |last5=Bassett |first5=Anne S. |date=January 2013 |title=Expression of autism spectrum and schizophrenia in patients with a 22q11.2 deletion |journal=Schizophrenia Research |volume=143 |issue=1 |pages=55–59 |doi=10.1016/j.schres.2012.10.010 |pmid=23153825 |s2cid=20964079}}</ref> Schizophrenia and autism are linked to the same gene deletion but manifest very differently from each other. The resulting phenotype depends on the stage of life at which the individual develops the disorder. Childhood manifestation of the gene deletion is typically associated with autism, while adolescent and later expression of the gene deletion often manifests in schizophrenia or other psychotic disorders.<ref>{{Cite news |date=2016-10-18 |title=Same DNA deletion paves paths to autism, schizophrenia {{!}} Spectrum |url=https://spectrumnews.org/opinion/viewpoint/dna-deletion-paves-paths-autism-schizophrenia/ |access-date=2016-11-13 |newspaper=Spectrum}}</ref> Though the disorders are linked by genetics, there is no increased risk found for adult schizophrenia in patients who are autistic.<ref name=":0" />

A 2013 study also genetically linked five psychiatric disorders, including schizophrenia and autism. The link was a [[Single-nucleotide polymorphism|single nucleotide polymorphism]] of two genes involved in [[Calcium channel|calcium channel signaling]] with [[neuron]]s. One of these genes, [[Cav1.2|CACNA1C]], has been found to influence [[cognition]]. It has been associated with autism, as well as linked in studies to schizophrenia and [[bipolar disorder]].<ref>{{Cite journal |last1=Roussos |first1=Panos |last2=McClure |first2=Margaret M. |last3=Hazlett |first3=Erin A. |last4=New |first4=Antonia S. |last5=Siever |first5=Larry J. |last6=Bitsios |first6=Panos |last7=Giakoumaki |first7=Stella G. |date=2013-03-30 |title=CACNA1C as a risk factor for schizotypal personality disorder and schizotypy in healthy individuals |journal=Psychiatry Research |volume=206 |issue=1 |pages=122–123 |doi=10.1016/j.psychres.2012.08.039 |pmc=4176879 |pmid=22985546}}</ref> These particular studies show clustering of these diseases within patients themselves or families.<ref>{{Cite web |title=Pleiotropy of psychiatric disorders will reinvent DSM |url=http://www.mdedge.com/currentpsychiatry/article/65079/practice-management/pleiotropy-psychiatric-disorders-will-reinvent#bib1 |access-date=2016-11-13 |website=www.mdedge.com}}</ref> The estimated [[heritability]] of schizophrenia is 70% to 90%,<ref>{{Cite journal |last1=Sullivan |first1=Patrick F. |last2=Kendler |first2=Kenneth S. |last3=Neale |first3=Michael C. |date=2003-12-01 |title=Schizophrenia as a complex trait: evidence from a meta-analysis of twin studies |journal=Archives of General Psychiatry |volume=60 |issue=12 |pages=1187–1192 |doi=10.1001/archpsyc.60.12.1187 |pmid=14662550 |doi-access=}}</ref> therefore the pleiotropy of genes is crucial since it causes an increased risk for certain psychotic disorders and can aid psychiatric diagnosis.

Through looping in three-dimensional space, distant non-coding regulatory elements, sometimes located several megabases away from gene promoters, can physically interact with and influence the expression of specific genes. For example, there is a genetic variant located upstream of the PCDH gene clusters that play a role in brain development and has  been shown to impact the expression of several [[protocadherin]] genes. These genes have been linked to schizophrenia (SCZ) and major depressive disorder (MDD).<ref name=":1" />