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Diagnostic Laboratories


Molecular Lab

CGH PicEstablished in 1993, the Hayward Genetics Center's Molecular Diagnostic Laboratory performs Fragile X by Southern analysis and PCR amplification. Please contact our laboratory for additional information at 504-988-5229. A lab test order form can be found at the end of this page.

The Molecular Diagnostic Laboratory is accredited by CAP (College of American Pathologists) and certified by CLIA (Clinical Laboratory Improvement Act 1988). The laboratory participates in regular internal and external quality assurance programs, including sample exchanges and proficiency testing.

Fragile X syndrome

Fragile X syndrome is the most common form of inherited mental retardation in human with an estimated incidence of 1 in 1,250 to 1 in 5,000 individuals.

Clinical features: Moderate mental retardation, long narrow face, large and protruding ears, macroorchidism and behavioral and emotional problems.

Inheritance: X-linked recessive inheritance. Males with full mutations are nearly always affected. Thirty to 50% of females with full mutations have signs and symptoms of the condition. Male premutation carriers (who are not affected) pass the mutation to all of their daughters and female premutation carriers have a 50% chance to pass the mutation to their daughters and sons. Full expansion from premutation to full mutation may only happen during the maternal transmission.

Normal:
5-40 repeats, not methylated

Gray zone:
41-55 repeats; not methylated. Occasionally alleles in this range expand like a premutation

Premutation:
56-200 repeats, not methylated.

Full mutation:
> 200 repeats, Methylated.

Indications:
1) Individuals with unexplained mental retardation, learning difficulties and/or autism.
2) Family history of mental retardation that is consistent with X-linked pattern of inheritance.

Test methodology: Our laboratory provides both PCR and southern blot based tests for the diagnosis of this common disease, which not only detects the sizes of the triplet repeats but also their methylation patterns. A package including both routine cytogenetics and molecular genetics studies is also available for patients with mental retardation.

Samples: Peripheral blood sample, solid tissues, and cultured amniocytes. CVS samples are not accepted due to the incompletion methylation of genes in early gestations. A maternal blood sample is required with prenatal testing, and will be tested at no extra charge if submitted at same time as proband.

Turnaround time: 2-4 weeks.

Package Study for mental retardation of unknown causes: In general, the package includes prometaphase chromosomal studies and DNA based molecular diagnosis for fragile X syndrome.

Southern Blot Analysis

A       B       C

Southern blot analysis of Fragile X syndrome to detect the sizes of the triplet repeats and their methylation pattern

Lane A: Fragile X patient with full CGG expansion and partial methylation

Lane B: Normal Female control

Lane C: Normal male control

 

1430 Tulane Ave, New Orleans, LA 70112 504-988-5263 medsch@tulane.edu