Sleeping Beauty transposon-based system for cellular reprogramming and targeted gene insertion in induced pluripotent stem cells.

The discovery of direct cell reprogramming and induced pluripotent stem (iPS) cell technology opened up new avenues for the application of non-viral, transposon-based gene delivery systems. The Sleeping Beauty (SB) transposon is highly advanced for versatile genetic manipulations in mammalian cells. We established iPS cell reprogramming of mouse embryonic fibroblasts and human foreskin fibroblasts by transposition of OSKM (Oct4, Sox2, Klf4 and c-Myc) and OSKML (OSKM + Lin28) expression cassettes mobilized by the SB100X hyperactive transposase. The efficiency of iPS cell derivation with SB transposon system was in the range of that obtained with retroviral vectors. Co-expression of the miRNA302/367 cluster together with OSKM significantly improved reprogramming efficiency and accelerated the temporal kinetics of reprogramming. The iPS cells displayed a stable karyotype, and hallmarks of pluripotency including expression of stem cell markers and the ability to differentiate into embryoid bodies in vitro. We demonstrate Cre recombinase-mediated exchange allowing simultaneous removal of the reprogramming cassette and targeted knock-in of an expression cassette of interest into the transposon-tagged locus in mouse iPS cells. This strategy would allow correction of a genetic defect by site-specific insertion of a therapeutic gene construct into 'safe harbor' sites in the genomes of autologous, patient-derived iPS cells.

[The prevalence of melanocytic naevi among teenagers]. / A festéksejtes anyajegyek elofordulása tinédzsereken.

UNLABELLED: Malignant melanoma is an increasing public health problem worldwide; accordingly, identification of the constitutional and environmental factors which contribute to the development of the disease, and hence identification of the individuals at high risk of melanoma, are indispensable steps in all primary prevention efforts. AIM: The objective of the present study was to assess the prevalence of different pigmented lesions among schoolchildren, and to investigate their relationship with phenotypic pigmentary characteristics, sun exposure and other factors. METHODS: A cross-sectional study was performed in two secondary schools in Szeged, Hungary. A total of 1320 schoolchildren, aged 14 to 18 years, underwent a whole-body skin examination. A standardized questionnaire was used to collect data on phenotypic, sun exposure and other variables. RESULTS: Between 1-10 common melanocytic naevi were found in 27% of the participants, and naevi numbers were in the range between 10-100 in 67%. 5.4% of them had more than 100 common melanocytic naevi. The prevalence of clinically atypical naevi was 24.3%. Congenital naevi were detected in 6.2% of the schoolchildren. A statistically significant association was found between the number of pigmented lesions and gender, hair colour, eye colour, skin phototype, the history of severe painful sunburns, and the family history of a large number of melanocytic naevi. CONCLUSIONS: Our study population displayed a markedly high prevalence of clinically atypical melanocytic naevi. Moreover, a considerable proportion of the investigated individuals had multiple common melanocytic naevi. Since the presence of large number of melanocytic naevi is a strong predictor for future melanoma development, health educational programmes on melanoma prevention should be aimed at young age groups.