The fragile X phenotype in a mosaic male with a deletion showing expression of the FMR1 protein in 28% of the cells

Am J Med Genet. 1996 Aug 9;64(2):302-8. doi: 10.1002/(SICI)1096-8628(19960809)64:2<302::AID-AJMG14>3.0.CO;2-J.


The instability of the CGG repeat region of FMR1 is not restricted to the CGG repeat but expands to flanking sequences as well. A mosaic fragile X male is reported with a deletion of part of the CGG repeat and 30 bp immediately 3' of the repeat, thus confirming the presence of a hotspot for deletions in the CGG region of FMR1. The deletion, detected in 28% of his lymphocytes, did not impair the transcription and translation of FMR1, suggesting that regulatory elements are not present in the deleted region. The patient has the characteristic fragile X phenotype and assuming that the mosaic pattern detected in the lymphocytes reflects the mosaic pattern in brain, 28% expression of FMRP may not be sufficient for normal cognitive functioning.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Base Sequence
  • Cells, Cultured
  • Fragile X Mental Retardation Protein
  • Fragile X Syndrome / genetics*
  • Humans
  • Lymphocytes / metabolism
  • Male
  • Molecular Sequence Data
  • Mosaicism*
  • Nerve Tissue Proteins / biosynthesis*
  • Nerve Tissue Proteins / genetics*
  • Polymerase Chain Reaction
  • Protein Biosynthesis
  • RNA-Binding Proteins*
  • Regulatory Sequences, Nucleic Acid
  • Sequence Deletion*
  • Transcription, Genetic
  • Trinucleotide Repeats*


  • FMR1 protein, human
  • Nerve Tissue Proteins
  • RNA-Binding Proteins
  • Fragile X Mental Retardation Protein

Associated data

  • GENBANK/S83512