Clinical involvement and protein expression in individuals with the FMR1 premutation
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F Tassone1, R J Hagerman, A K Taylor
1Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
Abstract:
Most individuals with the fragile X premutation are clinically unaffected; however, some show clinical manifestations, including learning difficulties, emotional problems, or even mental retardation. The basis of clinical involvement in these individuals is unknown. Premutation alleles are reportedly associated with normal levels of mRNA and protein (FMRP). To examine this issue in more detail, we studied six individuals with a premutation. We are reporting these cases to demonstrate a spectrum of phenotypic involvement which can be seen clinically. These cases include one individual with the premutation who has no evidence of FMR1 gene dysfunction but has mental retardation from other causes. Other cases presented here show varying degrees of FMR1 gene dysfunction as assessed by FMRP and FMR1 mRNA levels and various clinical features of fragile X. In two cases we observed a significant reduction in FMRP expression and an elevated FMR1 mRNA expression level associated with moderate cognitive deficit. Thus, the utilization of FMRP measures can be helpful in understanding for which premutation patients clinical involvement is caused by dysfunction of the FMR1 gene.
Insights
Most fragile X premutation carriers are unaffected, but some experience symptoms. Measuring Fragile X Messenger Ribonucleoprotein (FMRP) levels helps identify if FMR1 gene dysfunction causes clinical issues in these individuals.
Area of Science:
- Genetics
- Neuroscience
- Molecular Biology
Background:
- Fragile X premutation carriers are typically asymptomatic, but some exhibit clinical symptoms like learning difficulties or cognitive deficits.
- The underlying cause of clinical manifestations in premutation carriers remains unclear.
- Premutation alleles are generally associated with normal Fragile X Messenger Ribonucleoprotein (FMRP) levels.
Observation:
- This study investigated six individuals with the fragile X premutation to explore the spectrum of phenotypic involvement.
- One individual with the premutation had intellectual disability unrelated to FMR1 gene dysfunction.
- Other cases displayed varying degrees of FMR1 gene dysfunction, assessed by FMRP and FMR1 mRNA levels, alongside fragile X-associated clinical features.
Findings:
- Two cases showed significantly reduced FMRP expression coupled with elevated FMR1 mRNA levels.
- These two cases also presented with moderate cognitive deficits.
- FMRP levels serve as a useful biomarker for determining FMR1 gene dysfunction as the cause of clinical involvement in premutation patients.
Implications:
- Understanding the relationship between FMR1 gene dysfunction and clinical presentation in premutation carriers is crucial for accurate diagnosis.
- FMRP level assessment can aid in differentiating between fragile X-related symptoms and other causes of cognitive impairment.
- This research highlights the importance of molecular diagnostics in managing fragile X-associated disorders.
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