A novel deletion to normal size in the sperm of a fragile X full mutation male

Fig. 1. A deletion occurred in the sperm of a fragile X male. The proband is a 26-year-old Chinese male with moderate intellectual disability. Physical examination of the patient showed typical facial dysmorphism, including prominent large ears, elongated face, high-arched palate, crowded teeth, and macro-orchidism. Behavioural characteristics (poor eye-contact, hyperactivity/attention deficit hyperactivity disorder, seizure disorder, tactile defensiveness, aggressive behaviour and speech delay) were noted. (a) Southern blot of the blood DNA shows full mutations as three dominant bands above 5.8 kb whereas the sperm DNA shows a mosaic for premutation and a deletion. (b) Schematic representation, not drawn to scale, of the deletion found in the sperm. Flanking sequences of 6 bp at the 5′ end of the CGG repeat and part of the CGG repeat region were deleted (indicated by lower case letters), leaving seven pure CGG repeats consequently accompanying with intact ATG site. The EcoR I sites are indicated. The horizontal arrows indicate the extent of the deletion. The box indicates the CGG repeats that show partial deletion and that consists of pure CGG repeats. The ATG site and Chi-like element are indicated. (c) Polymerase chain reaction PCR analyses of duplicate sperm samples received at different time points (4 months away). The upper electropherogram shows mosaic for a premutation and deletion in the sperm and the bottom one shows the same mosaic pattern in another batch of sperm. (d) (PCR) analyses of DNA from the blood, buccal swab, and sperm of the subject. In the blood and buccal swab sample, products are obtained only from the full mutation alleles. In the sperm sample, however, both premutations ranging from 105 to 157 repeats and reduced alleles upto seven CGG repeats are obtained. (e) Exclusion of deletion in the premutation sized sperm. Lane 1 is the blood DNA sample from the patient’s mother. Lane 2 is the blood DNA from the patient. Lane 3 is the sperm sample from the patient. Lane 4 is a female control sample. PCR for lanes 1 to 4 is with primers specifically designed. The expected 155-bp fragment is successfully amplified in all samples, including the sperm DNA (lane 2). (f) CGG repeat primed PCR analysis of the maternal blood DNA. Capillary electrophoresis analysis shows that the mother is a premutation carrier of 80 CGG repeats with no AGG interruptions. disorders, affecting approximately 1 in 4000 newborn boys. CGG-repeat instability is the most common mutational mechanism that disrupts FMR1 expression and accounts for 95–99% of symptomatic mutations