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Objective: To explore the genetic basis for a pedigree affected with X-linked recessive mental retardation Claes-Jensen type., Methods: Genomic DNA was extracted from peripheral blood samples of the patient, his parents (phenotypically normal) and two elder brothers with similar clinical manifestations. Whole exome sequencing was carried out for the proband, and the result was verified by Sanger sequencing., Results: The proband was found to harbor a hemizygous c.1565C>T missense variant in exon 11 of the KDM5C gene. The transition has resulted in replacement of serine by phenylalanine at position 522 (p.Ser522Phe). Sanger sequencing showed that the patient's two elder brothers and mother carried the same variant, which was predicted to be probably damaging by SIFT, PolyPhen2 and Mutation_Taster. The three affected brothers presented with similar clinical phenotypes characterized by mental retardation, speech delay, behavioral problem, self-limited epilepsy responsible to medication, short stature and microcephaly. The mother only had mild cognitive impairment and learning disability. The same variant was not found in their father and was unreported previously., Conclusion: The c.1565C>T (p.Ser522Phe) of the KDM5C gene probably underlay the X-linked recessive mental retardation Claes-Jensen type in this pedigree.

Objective: To compare the efficiency of three different serotypes of adeno-associated virus (AAV) in mediating the transfection of enhanced green fluorescent protein (EGFP) in Tibet minipig fetal fibroblasts (PFFs)., Methods: Three recombinant AAV of different serotypes encoding EGFP were constructed and transfected into primary cultured PFFs at the multiplicity of infection (MOI) ranging from 10(3) to 10(5). The expression rates of EGFP in the PFFs were assessed 72 h after the infection by flow cytometry, and the transfected PFFs were observed under inverted fluorescence microscope. The toxicity of AAVs to PFFs was analyzed using MTT assay., Results: The transfection efficiency of AAV2-EGFP increased with MOI. At the MOI of 10(3), the transfection efficiency of AAV2-EGFP was (33.68∓1.18)%, which increased to (50.80∓2.59)% at the MOI of 10(4) but without obvious further increase at the MOI of 10(5). The other two serotypes of the virus (AAV8 and AAV9) showed no obvious changes in the infection efficiency at any MOIs. The transfection efficiency of AAV8 was (8.3∓0.02)% and that of AAV9 was (2.20∓1.02)% at the MOI of 10(5). Transfection with the 3 viruses caused no adverse effects on the normal cell growth of the PFFs., Conclusions: AAV2 has a significantly higher infection rate in cultured PFFs than AAV8 and AAV9, and the latter two have a rather low infection efficiency. All the three AAVs have no cell toxicity to the PFFs.