Molecular fragile X screening in normal populations

Abstract

In December, 1993, we initiated a pilot project in which DNA fragile X (fraX) testing was offered during routine prenatal or genetic counseling to all pregnant women seen at the Genetics & IVF Institute, most of whom were referred for the indication of advanced maternal age. A brochure on fragile X syndrome was sent to each patient prior to her appointment and was reviewed by a counselor or physician during the counseling session. As of June 1995, 3,345 patients were offered testing; 474 women with no identified family history of mental retardation or learning disability and 214 women with a positive family history accepted the test on a self‐pay basis. The second population screened was 271 potential donors in our anonymous egg donor program. DNA from blood was tested by Southern blot using EcoRI/EagI and StB12.3. If an expansion was detected, CGG repeat number was determined by PCR‐based analysis. Among the 474 patients with unremarkable family histories, three fraX carriers were identified (repeat sizes = 60+), whereas none were found in the 214 patients with a positive family history. Among the potential egg donors, two high borderline patients were identified (repeat sizes = between 50 and 59). Our ongoing study indicates that screening of pregnant or preconceptual populations for fraX carrier status using DNA testing is accepted by many patients and is an important addition to current medical practice. © 1996 Wiley‐Liss, Inc.

Genetic evaluation of oocyte donors: recipient couple preferences and outcome of testing

“…However, it appears reasonable to include fragile X testing among the recommended tests for egg donors, given the implications of abnormal testing, its relatively high frequency in the general population, and the fact that carriers in the egg donor pool may not yet have developed diminished ovarian reserve because of their young age. Fragile X testing of egg donors has been advocated by some in the past (10). According to the ASRM 2006 Minimum Genetic Screening for Gamete Donors, fragile X testing may be performed at the discretion of the individual program (2).…”

Evaluation of the fragile X (FRAXA) syndrome with methylation-sensitive PCR

“…The small amount of DNA needed for our MS-PCR test is advantageous for many purposes, such as for prenatal diagnosis, for the analysis of DNA extracted from Guthrie cards, and for studies from small tissue samples obtainable from fine needle biopsies (Pai et al 1994;Dawson et al 1995;Brown et al 1996;Abrams et al 1999;Spence et al 1996;Larsen et al 1997). Moreover, it may facilitate non-invasive diagnosis from hair bulbs and buccal smears.…”

“…Currently available procedures for the diagnostic evaluation of the FRAXA syndrome include cytogenetic, Southern-blot, polymerase chain reaction (PCR), reverse transcription PCR (RT-PCR), and immunohistochemical analyses (Rousseau et al 1991a;Brown et al 1993;Cao et al 1994;Pai et al 1994;El-Aleem et al 1995;Wang et al 1995;Carrel and Willard 1996;Haddad et al 1996;Holden et al 1996;Spence et al 1996;Willemsen and Oostra 2000). The most commonly applied molecular geneticbased techniques depend on either the detection of the expanded repeat, the de novo methylation of the affected gene regions, or both (Brown et al 1993;Cao et al 1994;Pai et al 1994;El-Aleem et al 1995;Wang et al 1995;Carrel and Willard 1996;Haddad et al 1996;Holden et al 1996;Spence et al 1996;Hecimovic et al 1997;Panagopoulos et al 1999;Strelnikov et al 1999).…”

“…The most commonly applied molecular geneticbased techniques depend on either the detection of the expanded repeat, the de novo methylation of the affected gene regions, or both (Brown et al 1993;Cao et al 1994;Pai et al 1994;El-Aleem et al 1995;Wang et al 1995;Carrel and Willard 1996;Haddad et al 1996;Holden et al 1996;Spence et al 1996;Hecimovic et al 1997;Panagopoulos et al 1999;Strelnikov et al 1999). Only radioactive or non-radioactive Southern-blotting of DNA doubledigested with methyl-sensitive and methyl-insensitive restriction enzymes is able reliably to cover the whole spectrum of premutations, full mutations, and mosaicism that may be encountered in the context of this syndrome (Brown et al 1993;Kolehmainen and Karant 1994;Kirchgessner et al 1995;Allingham-Hawkins et al 1996;Carrel and Willard 1996;de Vries et al 1998).…”

In the Gray Zone in the Fragile X Gene: What are the Key Unanswered Clinical and Biological Questions?

“…of PatientsLocationGray Zone Rate (%)Rousseau et al5635–54Not reportedWomen10,624Canada0.4Dawson et al5740–59NewbornsMen and women2,000Spain2.7Zhong et al5841–54Not reportedMen56USA1.7Spence et al5940–59(Pregnant women of advanced maternal age)Women745USA2.2Drasinover et al5250–55Not reportedWomen10,587Israel0.5Dombrowski et al6040–54Not reportedMen10,572Canada0.3Penagarikano et al2241–54Not reportedMen158Spain3.2Cronister et al6145–54…”