Expression profiling of human melanocytes in response to UV-B irradiation.

A comprehensive gene expression analysis of human melanocytes was performed assessing the transcriptional profile of dark melanocytes (DM) and light melanocytes (LM) at basal conditions and after UV-B irradiation at different time points (6, 12 and 24 h), and in culture with different keratinocyte-conditioned media (KCM + and KCM -). The data, previously published in [1], have been deposited in NCBI's Gene Expression Omnibus (GEO accession number: GSE70280).

Comparison of the Transcriptional Profiles of Melanocytes from Dark and Light Skinned Individuals under Basal Conditions and Following Ultraviolet-B Irradiation.

We analysed the whole-genome transcriptional profile of 6 cell lines of dark melanocytes (DM) and 6 of light melanocytes (LM) at basal conditions and after ultraviolet-B (UVB) radiation at different time points to investigate the mechanisms by which melanocytes protect human skin from the damaging effects of UVB. Further, we assessed the effect of different keratinocyte-conditioned media (KCM+ and KCM-) on melanocytes. Our results suggest that an interaction between ribosomal proteins and the P53 signaling pathway may occur in response to UVB in both DM and LM.

Melanocytes from dark and light skin respond differently after ultraviolet B irradiation: effect of keratinocyte-conditioned medium.

Background/purpose: The response to the damage provoked by exposure to UV radiation is mediated by melanocytes and a network of paracrine factors produced by keratinocytes, and it varies among individuals of different geographical origin and skin colour. The mechanisms underlying this differential response, however, have not been completely elucidated.

Methods: We characterized the differential behaviour of melanocytes (proliferation and differentiation/melanogenesis) from both dark- and light-skinned individuals in response to ultraviolet B (UVB) irradiation, cultured with and without keratinocyte-conditioned medium (KCM).

The interplay between natural selection and susceptibility to melanoma on allele 374F of SLC45A2 gene in a South European population.

We aimed to study the selective pressures interacting on SLC45A2 to investigate the interplay between selection and susceptibility to disease. Thus, we enrolled 500 volunteers from a geographically limited population (Basques from the North of Spain) and by resequencing the whole coding region and intron 5 of the 34 most and the 34 least pigmented individuals according to the reflectance distribution, we observed that the polymorphism Leu374Phe (L374F, rs16891982) was statistically associated with skin color variability within this sample. In particular, allele 374F was significantly more frequent among the individuals with lighter skin.

Simultaneous purifying selection on the ancestral MC1R allele and positive selection on the melanoma-risk allele V60L in south Europeans.

In humans, the geographical apportionment of the coding diversity of the pigmentary locus melanocortin-1 receptor (MC1R) is, unusually, higher in Eurasians than in Africans. This atypical observation has been interpreted as the result of purifying selection due to functional constraint on MC1R in high UV-B radiation environments. By analyzing 3,142 human MC1R alleles from different regions of Spain in the context of additional haplotypic information from the 1000 Genomes (1000G) Project data, we show that purifying selection is also strong in southern Europe, but not so in northern Europe.

My dog's cheeks: A PBL project on collagen for cell biology and genetics courses.

Students often have an oversimplified view of biological facts, which may hinder subsequent understanding when conceptual complexity gives rise to cognitive conflicts. To avoid this situation here, we present a PBL approach for the analysis of Ehlers-Danlos syndrome (EDS), which integrates a variety of topics in cell biology, genetics, and molecular biology, and it is used to illustrate the inherent complexities in some classical biological concepts. Students of two different courses analyze phenotypic, cellular, and molecular characteristics of EDS.

Paternity testing in a PBL environment.

Problem Based Learning (PBL) makes use of real-life scenarios to stimulate students' prior knowledge and to provide a meaningful context that is also related to the student's future professional work. In this article, Paternity testing is presented using a PBL approach that involves a combination of classroom, laboratory, and out-of-class activities: in relation to a fictitious newborn found on the Campus, students design a PCR based protocol to determine their own genotype for two markers. Pooled class genotypes serve to calculate allelic frequencies and to assess Hardy-Weinberg equilibrium.

The diversity profile of TP53 is influenced by positive selection on the immediately upstream locus WDR79.

Background/aim: TP53 is an efficient central node in a signal transduction network that responds to minimize cancer. However, over 50% of tumors show some mutation in TP53. Thus, one might argue that this single central node network lacks robustness.

Complex signatures of selection for the melanogenic loci TYR, TYRP1 and DCT in humans.

Background: The observed correlation between ultraviolet light incidence and skin color, together with the geographical apportionment of skin reflectance among human populations, suggests an adaptive value for the pigmentation of the human skin. We have used Affymetrix U133a v2.0 gene expression microarrays to investigate the expression profiles of a total of 9 melanocyte cell lines (5 from lightly pigmented donors and 4 from darkly pigmented donors) plus their respective unirradiated controls.