title: Phenotypic spectrum in uniparental disomy: Low incidence or lack of study?
abstract: BACKGROUND
  Alterations in the human chromosomal complement are expressed phenotypically ranging from (i) normal, via (ii) frequent fetal loss in otherwise normal person, to (iii) sub-clinical to severe mental retardation and dysmorphism in live births. A subtle and microscopically undetectable chromosomal alteration is uniparental disomy (UPD), which is known to be associated with distinct birth defects as per the chromosome involved and parental origin. UPD can be evident due to imprinted genes and/or activation of recessive mutations.
  
  
  OBJECTIVE
  The present study comprises of data mining of published UPD cases with a focus on associated phenotypes. The goal was to identify non-random and recurrent associations between UPD and various genetic conditions, which can possibly indicate the presence of new imprinted genes.
  
  
  METHODS
  Data mining was carried out using the homepage "http://www.fish.uniklinikum-jena.de/UPD.html.", an online catalog of published cases with UPD.
  
  
  METHODS
  The UPD cases having normal karyotype and with or without clinical findings were selected to analyze the associated phenotypes for each chromosome, maternal or paternal involved in UPD.
  
  
  RESULTS
  Our results revealed many genetic conditions (other than the known UPD syndromes) to be associated with UPD. Even in cases of bad obstetric history as well as normal individuals chance detection of UPD has been reported.
  
  
  CONCLUSIONS
  The role of UPD in human genetic disorders needs to be studied by involving larger cohorts of individuals with birth defects as well as normal population. The genetic conditions were scrutinized in terms of inheritance patterns; majority of these were autosomal recessive indicating the role of UPD as an underlying mechanism.
authors: Institute of Science, Nirma University, Ahmedabad, Gujarat, India.
authors: Arpan D
authors: AD
authors: Bhatt
authors: Thomas
authors: T
authors: Liehr
authors: Sonal R
authors: SR
authors: Bakshi
keywords: Autosomal recessive; birth defects; data mining; phenotypic expression; uniparental disomy