Chromosome 7

Individuals who carry an extra copy of 7q11.23, the genetic region on chromosome 7 that is missing in those with Williams syndrome, have language impairments and other autism-like social difficulties.

Relevance to autism:

Although deletion of 7q11.23 leads to Williams syndrome, duplication of the region resembles autism. Of 14 children with 7q11.23 duplication syndrome, all have problems speaking, 7 have mild or moderate mental retardation, and 6 have either been formally diagnosed with autism or have autism-like features, such as poor eye contact or trouble with social interactions1.

GTF21, a gene within the 7q11.23 region, interacts with DLX5 and DLX6 — transcription factors implicated in autism2.

Other autism-implicated genes on chromosome 7 include AUTS2, CNTNAP2 and FOXP2. AUTS2 has been linked to autism in various gene association studies3.

A 2010 study shows that a variant of CNTNAP2 may alter the brain to emphasize connections between nearby regions and diminish those between more distant ones4.

Variants in CNTNAP2 also affect the timing of language development in the general population5.

FOXP2 is linked to language development and regulates CNTNAP2 gene expression

Williams syndrome:

Deletion of the 7q11.2 region leads to the autism-related disorder, Williams syndrome. Children with Williams syndrome have a range of cognitive symptoms, including a happy and highly social demeanor, developmental delay and strong language skills. They also have cardiovascular symptoms and facial dysmorphology, such as a small nose with a flattened bridge and a small chin6.

GTF2I is one of a handful of genes that researchers consider to be key players in Williams syndrome. The protein it encodes is a transcription factor, affecting the expression of other genes, but its precise role is unknown7.

One child with Williams syndrome lacks one copy of all the genes on the 7q11.2 region except for GTF21, for which she has two functional copies. The girl has facial features characteristic of Williams syndrome and a heart defect, but no developmental delay. By the time the girl was 2 years old, her caretakers confirmed that she has normal social behavior: She is shy around strangers and doesn’t stare at other people’s eyes.


References:
  1. Van der Aa N. et al. Eur. J. Med. Genet. 52, 94-100 (2009) Pubmed
  2. Poitras L. et al. Development 137, 3089-3097 (2010) Pubmed
  3. Sultana R. et al. Genomics 80, 129-134 Pubmed
  4. Scott-Van Zeeland A. et al. Sci. Transl. Med. 2, 56-80 (2010) Pubmed
  5. Whitehouse A. et al. Genes Brain Behav. 10, 451-456 (2011) Pubmed
  6. Feyder M. et al. Am. J. Psychiatry 167, 1508-1517 (2010) Pubmed
  7. Sakurai T. et al. Autism Res., Epub ahead of print (2010) Pubmed
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