title: [Analysis of CGG repeat instability in germline cells from two male fetuses affected with fragile X syndrome].
abstract: OBJECTIVE
  To study the pattern of CGG repeat instability within germline cells derived from two male fetuses affected with Fragile X syndrome (FXS).
  
  
  METHODS
  The length and methylation status of CGG repeats within the testes of a fetus carrying a full FXS mutation and another fetus carrying mosaicism FXS mutation were analyzed with Southern blotting and AmplideX FMR1 PCR. Immunohistochemistry was also applied for the measurement of FMR1 protein (FMRP) expression within the testes.
  
  
  RESULTS
  For the fetus carrying the full mutation, Southern blotting analysis of the PCR product has detected an expected band representing the full mutation in its brain and a premutation band of > 160 CGG repeats in its testis. Whereas the pattern of premutation/full mutation in mosaic testis was similar to that in peripheral blood and no sign of contracted fragment was found other than a band of about 160 CGG repeats. Immunohistochemistry assay with a FMRP-specific antibody demonstrated a number of FMRP-positive germ cells, which suggested a contraction from full mutation to premutation alleles.
  
  
  CONCLUSIONS
  This study has clarified the instability pattern of CGG repeat and expression of FMRP protein within the testes of fetuses affected with FXS, confirming that the CGG repeat can contract progressively within the germline. The FMRP expression in the testis is consistent with spermatogonium proliferation, and thus the contraction from full mutation to unmethylated premutations may occur for the requirement of FMRP expression during spermatogenesis. The better understanding of FMRP function during germ cell proliferation may elucidate the mechanism underlying the contraction of full FXS mutation in male germline.
authors: State Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, Hunan 410078, China. Email: wulingqian@sklmg.edu.cn.
authors: Ranhui
authors: R
authors: Duan
authors: Shiyu
authors: S
authors: Luo
authors: Wen
authors: W
authors: Huang
authors: Haoxian
authors: H
authors: Li
authors: Ying
authors: Y
authors: Peng
authors: Qian
authors: Q
authors: Du
authors: Lingqian
authors: L
authors: Wu
mesh_terms: D000025:Abortion, Eugenic; D015139:Blotting, Southern; D001921:Brain / Q000196:embryology / Q000378:metabolism; D019175:DNA Methylation; D017809:Fatal Outcome; D005333:Fetus / Q000166:cytology / Q000378:metabolism*; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics* / Q000378:metabolism; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D009030:Mosaicism; D009154:Mutation; D016133:Polymerase Chain Reaction; D013094:Spermatozoa / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D019680:Trinucleotide Repeat Expansion / Q000235:genetics*
chemical_list: D051860:Fragile X Messenger Ribonucleoprotein 1; C497683:FMR1 protein, human