From the Guidelines
The parental origin of the genotype in Turner's syndrome (TS) is typically a loss of the paternal X chromosome, resulting in a 45,X genotype.
Key Points
- Turner syndrome is a genetic disorder that affects females, resulting from the partial or complete loss of one X chromosome [ 1 ].
- The most common karyotype associated with Turner syndrome is 45,X, which accounts for approximately 50% of cases [ 1 ].
- The loss of the paternal X chromosome is more common than the loss of the maternal X chromosome in Turner syndrome [ 1 ].
- The exact mechanism of X chromosome loss in Turner syndrome is not fully understood, but it is thought to occur during meiosis or early embryonic development [ 1 ].
- Mosaicism, where a mixture of 45,X and 46,XX cells are present, can also occur in Turner syndrome, and may be associated with a milder phenotype [ 1 ].
Clinical Implications
- Turner syndrome is associated with an increased risk of cardiovascular disease, including aortic dilation and dissection [ 1 ].
- Regular cardiac monitoring and surveillance are essential for individuals with Turner syndrome to detect and manage cardiovascular complications early [ 1 ].
- A comprehensive understanding of the genetic and molecular mechanisms underlying Turner syndrome is crucial for the development of effective diagnostic and therapeutic strategies [ 1 ].
From the Research
Parental Origin of Genotype in Turner's Syndrome
- The parental origin of the single X chromosome in Turner syndrome has been studied, and the results show that the majority of individuals retain a maternal X (Xm) chromosome 2, 3, 4, 5.
- The ratio of maternal X to paternal X is approximately 2:1, which is consistent with the expected proportion of meiotic or mitotic products, with equal loss at each step, given the nonviability of 45,Y 2.
- Studies have found that 60-80% of the X chromosomes are maternal in origin 4, and 74% of the 45,X patients have a maternal X chromosome 5.
- The parental origin of the X chromosome may influence certain phenotypic traits, such as kidney malformations, ocular abnormalities, and aortic stiffness 3, 6.
- The majority of isochromosome Xq and ring/marker X chromosomes are equally likely to result from both maternal and paternal meiotic errors, while deletions and abnormal Y chromosomes are more likely to be paternal in origin 4, 5.
Comparison of Maternal and Paternal X Chromosomes
- Individuals with a maternal X chromosome (Xm) may have a higher risk of certain complications, such as kidney malformations and aortic stiffness 3, 6.
- Those with a paternal X chromosome (Xp) may have a higher incidence of ocular abnormalities and higher academic achievement 3.
- The response to growth hormone therapy is comparable between individuals with Xm and Xp chromosomes 3.