OBJECTIVE: To explore the genetic basis for a child with Rothmund-Thomson syndrome (RTS). METHODS: The child has featured poikeloderma, short stature, cataract, sparse hair and skeletal malformation. Peripheral blood samples of the child and her family members were collected and subjected to whole exome sequencing. Candidate variants were verified by Sanger sequencing. RESULTS: The child was found to harbor compound heterozygous variants of the RECQL4 gene, namely c.1048_1049delAG and c.2886-1G>A, among which c.2886-1G>A was unreported previously. According to the ACMG guidelines, the c.1048_1049delAG was predicted to be pathogenic (PVS1+PM3_Strong+PM2), while the c.2886-1G>A was predicted to be likely pathogenic (PVS1+PM2). CONCLUSION The compound heterozygous variants of the RECQL4 gene probably underlay the pathogenesis of RTS in this patient. Above finding has enriched the mutational spectrum of the RECQL4 gene.
Child ; Family ; Female ; Humans ; Mutation ; RecQ Helicases/genetics* ; Rothmund-Thomson Syndrome/genetics* ; Whole Exome Sequencing

The defect or block of apoptosis is an important factor involved in the drug resistance of tumor cells. Blm gene plays a great role in DNA damage and repair. This study was aimed to explore the relationship of blm gene expression with cell cycle and apoptosis after Jurkat DNA damage. The apoptosis rate and change of cell cycle were detected by flow cytometry, the expression level of blm mRNA in Jurkat cells was determined by semi-quantitative RT-PCR. The results indicated that after induction with 0.4 g/L of mitomycin C (MMC) for 24 hours the apoptosis rate of Jurkat cells were (11.42±0.013)%, and (66.08±1.60)% Jurkat cells were arrested in G2/M phase. After induction for 48 hours, the apoptosis rate of Jurkat cells declined from (11.42±0.013)% to (8.08±0.27)%, and cell count of Jurkat cells arrested in G2/M phase decreased from (66.08±1.60)% to (33.96±1.05)%. When induced with 0.4 g/L of MMC for 24 hours, the apoptosis rate of fibroblasts and the percentage of fibroblasts in G2/M, G0-G1 and S phase all showed no significant change until 48 hours. The range of apoptosis rate and the change of cell percentage in three phases were significantly different between Jurkat cells and fibroblasts (p<0.01). Expression level of blm mRNA in Jurkat cells was remarkably higher than that in normal fibroblasts (p<0.01), at 48 hours expression level of blm mRNA was remarkably higher than that at 24 hours. The 2 groups showed clear difference of blm mRNA expression after treated by MMC (p<0.01). It is concluded that the blm gene may play a significant role in repair of DNA damage of Jurkat cells after MMC induction. Abnormal expression of blm is correlated to the drug resistance of leukemia cells.
Apoptosis ; Cell Cycle ; DNA Damage ; drug effects ; DNA Repair ; drug effects ; Humans ; Jurkat Cells ; Mitomycin ; pharmacology ; RecQ Helicases ; genetics

RecQ5 in mammalian cells has been suggested to suppress inappropriate homologous recombination. However, the specific pathway(s) in which it is involved and the underlining mechanism(s) remain poorly understood. We took advantage of genetic tools in Drosophila to investigate how Drosophila RecQ5 (dRecQ5) functions in vivo in homologous recombination-mediated double strand break (DSB) repair. We generated null alleles of dRecQ5 using the targeted recombination technique. The mutant animals are homozygous viable, but with growth retardation during development. The mutants are sensitive to both exogenous DSB-inducing treatment, such as gamma-irradiation, and endogenously induced double strand breaks (DSBs) by I-Sce I endonuclease. In the absence of dRecQ5, single strand annealing (SSA)-mediated DSB repair is compromised with compensatory increases in either inter-homologous gene conversion, or non-homologous end joining (NHEJ) when inter-chromosomal homologous sequence is unavailable. Loss of function of dRecQ5 also leads to genome instability in loss of heterozygosity (LOH) assays. Together, our data demonstrate that dRecQ5 functions in SSA-mediated DSB repair to achieve its full efficiency and in suppression of LOH in Drosophila.
Animals ; DNA Repair ; genetics ; DNA, Single-Stranded ; genetics ; Drosophila Proteins ; genetics ; metabolism ; Drosophila melanogaster ; genetics ; metabolism ; Loss of Heterozygosity ; genetics ; RecQ Helicases ; genetics ; metabolism

RecQ is a highly conserved helicase necessary for maintaining genome stability in all organisms. Genome comparison showed that a homologue of RecQ in Deinococcus radiodurans designated as DR1289 is a member of RecQ family with unusual domain arrangement: a helicase domain, an RecQ C-terminal domain, and surprisingly three HRDC domain repeats, whose function, however, remains obscure currently. Using an insertion deletion, we discovered that the DRRecQ mutation causes an increase in gamma radiation, hydroxyurea and mitomycine C and UV sensitivity. Using the shuttle plasmid pRADK, we complemented various domains of the D. radiodurans RecQ (DRRecQ) to the mutant in vivo. Results suggested that both the helicase and helicase-and-RNase-D-C-terminal (HRDC) domains are essential for complementing several phenotypes. The complementation and biochemical function of DRRecQ variants with different domains truncated in vitro suggested that both the helicase and three HRDC domains are necessary for RecQ functions in D. radiodurans, while three HRDC domains have a synergistic effect on the whole function. Our finding leads to the hypothesis that the RecF recombination pathway is likely a primary path of double strand break repair in this well-known radioresistant organism.
Amino Acid Sequence ; Deinococcus ; enzymology ; genetics ; Molecular Sequence Data ; Mutation ; genetics ; Phenotype ; Protein Structure, Tertiary ; RecQ Helicases ; chemistry ; genetics ; metabolism ; Sequence Alignment ; Sequence Homology, Amino Acid

The mutations of BLM gene may result in Bloom's syndrome which includes immunodeficiency, predisposition to malignant tumors and so on, and enhances sister chromati exchange (SCE), DNA replication failure, genome instability, and increases cancer susceptibility. This study was aimed to investigate the variability of mRNA expression level and cDNA structure of BLM gene in tumor cell strains so as to look for a new cancerogenic mechanism and to find a new therapeutic target. The expression level of mRNA and the structure of cDNA of BLM gene in six tumor cell strains and the normal human bone marrow mononuclear cells were detected with RT-PCR and DNA sequencing was performed. The results indicated that these tumors cells expressed BLM mRNA higher than the normal human bone marrow mononuclear cells (P < 0.01), but no cDNA sequence abnormality of BLM gene in these tumors cells was observed. It is concluded that the increase of expressing level of BLM mRNA may play an important role in the development of these tumors.
Base Sequence ; Cell Line, Tumor ; DNA Helicases ; genetics ; Gene Expression Regulation, Neoplastic ; HL-60 Cells ; Humans ; Jurkat Cells ; Molecular Sequence Data ; RNA, Messenger ; biosynthesis ; genetics ; RecQ Helicases ; Reverse Transcriptase Polymerase Chain Reaction ; Sequence Analysis, DNA