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Gene Dosage Track Legend

Literature regarding all the genes on chromosome 18 is reviewed on an annual basis. As the understanding of the effects of gene copy number changes evolves, the gene dosage codes will be updated to reflect the latest knowledge. Therefore most all classifications are provisional based on the most current data.

Hemizygosity classes

  1. No clinical effect – due to hemizygosity (genes indicated in blue)
    • There is a measurable effect but without clinical significance
    • CNV in multiple individuals or normal human knockouts identified
    • Null mouse has no abnormal phenotype
    • Heterozygous knockout mouse has no abnormal phenotype
  2. Risk factor for disease from hemizygosity but only in combination with multiple genetic or environmental factors (genes indicated in green)
  3. Conditional cause of disease from hemizygosity but only in the presence of another specific genetic or environmental risk factor. (genes indicated in purple)
    • Trans – a mutation in another gene
    • Cis – a mutation in the remaining copy; a revealed recessive mutation
    • Environmental – phenotype only present in conjunction with an environmental factor
  4. Low penetrance disease occurring in fewer than 50% of people with hemizygosity. (genes indicated in orange)
  5. Causal of disease if hemizygous with a penetrance of at least 50% (genes indicated in pink)
    • Based on our study data
    • Based on data from the heterozygous knockout mouse
    • Based on human disease literature
  6. Haplolethal (genes indicated red)
    • Knock-out mouse hemizygous prenatal lethal
    • In a critical region never found in hemizygosity in people
  7. Unknown – no data are available regarding the effect of hemizygosity or heterozygous loss of function

Suprazygosity classes

  1. No clinical effect (genes indicated in blue)
    • There is a measurable effect but without clinical significance
    • Whole gene CNV in multiple unaffected people
    • Transgenic mouse has no abnormal phenotype
  2. Risk factor in disease from suprazygosity but only in combination with multiple genetic or environmental factors. (genes indicated in green)
  3. Conditional cause of disease from suprazygosity but only in the presence of another specific genetic (trans) or environmental risk factor. (genes indicated in purple)
  4. Low penetrance disease occurring in fewer than 50% of people with gene duplication. (genes indicated in orange)
  5. Causal of disease if suprazygous with a penetrance of at least 50% (genes indicated in pink)
  6. Unknown – no data are available regarding the effect of suprazygosity or gain of function. (genes indicated in gray)