Monozygotic twins of opposite sex.
Although discordant karyotypes are known in identical twins, cases involving differences in sex phenotype are rare. We studied identical twins with the 46,XY karyotype - a male with mixed gonadal dysgenesis and a female with "pure" gonadal dysgenesis. The testis-determining SRY gene was present in DNA from both twins but no mutations were detected in the SRY conserved motif. Monozygosity was indicated by short tandem repeat polymorphism analysis. These observations could be attributed to (i) mutation and mosaicism involving "downstream" sex-determining loci, (ii) variable penetrance of genes such as DSS/NR0B1, duplication of which can disrupt the male-determining pathway, or (iii) occurrence of cryptic 45,X gonadal cell lines.
Wachtel
S S
SS
Division of Reproductive Genetics, Department of Obstetrics and Gynecology, University of Tennessee, Memphis TN 38103, USA. swatchtel@utmem.edu
Somkuti
S G
SG
Schinfeld
J S
JS
D000293:Adolescent; D017124:Conserved Sequence / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D005260:Female; D006059:Gonadal Dysgenesis / Q000235:genetics* / Q000503:physiopathology; D006060:Gonadal Dysgenesis, Mixed / Q000235:genetics / Q000503:physiopathology; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009030:Mosaicism / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins; D019683:Penetrance; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012727:Sex Characteristics; D019849:Sex Determination Processes; D012733:Sex Differentiation / Q000235:genetics*; D051876:Sex-Determining Region Y Protein; D020080:Tandem Repeat Sequences / Q000235:genetics; D014157:Transcription Factors; D014430:Twins, Monozygotic / Q000235:genetics*
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors