Gene Expression in Trypanosomatid Parasites

The parasites Leishmania spp., Trypanosoma brucei, and Trypanosoma cruzi are the trypanosomatid protozoa that cause the deadly human diseases leishmaniasis, African sleeping sickness, and Chagas disease, respectively. These organisms possess unique mechanisms for gene expression such as constitutive polycistronic transcription of protein-coding genes and trans-splicing. Little is known about either the DNA sequences or the proteins that are involved in the initiation and termination of transcription in trypanosomatids. In silico analyses of the genome databases of these parasites led to the identification of a small number of proteins involved in gene expression. However, functional studies have revealed that trypanosomatids have more general transcription factors than originally estimated. Many posttranslational histone modifications, histone variants, and chromatin modifying enzymes have been identified in trypanosomatids, and recent genome-wide studies showed that epigenetic regulation might play a very important role in gene expression in this group of parasites. Here, we review and comment on the most recent findings related to transcription initiation and termination in trypanosomatid protozoa

Transcription of Leishmania major U2 small nuclear RNA gene is directed by extragenic sequences located within a tRNA-like and a tRNA-Ala gene

Sequence comparisons of U2 snRNA genes and flanking regions from T. cruzi (CL Brener Non-Esmeraldo-like). Sequences from the genes located on chromosomes 23, 37 and 6 are shown. The U2 snRNA gene from chromosome 23 is presented in blue font. The position of boxes A and B is indicated. Sequence numbers are relative to the TSS (+1) from the U2 snRNA. (PDF 1404 kb

Gene organization and sequence analyses of transfer RNA genes in Trypanosomatid parasites

<p>Abstract</p> <p>Background</p> <p>The protozoan pathogens <it>Leishmania major</it>, <it>Trypanosoma brucei </it>and <it>Trypanosoma cruzi </it>(the Tritryps) are parasites that produce devastating human diseases. These organisms show very unusual mechanisms of gene expression, such as polycistronic transcription. We are interested in the study of tRNA genes, which are transcribed by RNA polymerase III (Pol III). To analyze the sequences and genomic organization of tRNA genes and other Pol III-transcribed genes, we have performed an <it>in silico </it>analysis of the Tritryps genome sequences.</p> <p>Results</p> <p>Our analysis indicated the presence of 83, 66 and 120 genes in <it>L. major, T. brucei </it>and <it>T. cruzi</it>, respectively. These numbers include several previously unannotated selenocysteine (Sec) tRNA genes. Most tRNA genes are organized into clusters of 2 to 10 genes that may contain other Pol III-transcribed genes. The distribution of genes in the <it>L. major </it>genome does not seem to be totally random, like in most organisms. While the majority of the tRNA clusters do not show synteny (conservation of gene order) between the Tritryps, a cluster of 13 Pol III genes that is highly syntenic was identified. We have determined consensus sequences for the putative promoter regions (Boxes A and B) of the Tritryps tRNA genes, and specific changes were found in tRNA-Sec genes. Analysis of transcription termination signals of the tRNAs (clusters of Ts) showed differences between <it>T. cruzi </it>and the other two species. We have also identified several tRNA isodecoder genes (having the same anticodon, but different sequences elsewhere in the tRNA body) in the Tritryps.</p> <p>Conclusion</p> <p>A low number of tRNA genes is present in Tritryps. The overall weak synteny that they show indicates a reduced importance of genome location of Pol III genes compared to protein-coding genes. The fact that some of the differences between isodecoder genes occur in the internal promoter elements suggests that differential control of the expression of some isoacceptor tRNA genes in Tritryps is possible. The special characteristics found in Boxes A and B from tRNA-Sec genes from Tritryps indicate that the mechanisms that regulate their transcription might be different from those of other tRNA genes.</p

Impact of the COVID-19 Pandemic on the Diagnosis and Prognosis of Melanoma

Background: Early detection of melanoma is one of the main diagnostic goals of dermatologists worldwide, due to the increasing incidence of the disease in our environment. However, the irruption of the SARS-CoV-2 pandemic has posed a challenge to global healthcare, forcing systems to focus their resources on the fight against COVID-19. Methods: Retrospective cohort study. The exposed cohort were patients diagnosed with melanoma in the year after the general confinement in Spain (15 March 2020) and the unexposed cohort were patients with melanoma diagnosed in the previous year. Results: 130 patients were included. No differences were observed between demographic characteristics in both cohorts. The mean Breslow of melanoma before the onset of the pandemic was 1.08, increasing to 2.65 in the year after the onset of the pandemic (p < 0.001). On the other hand, the percentage of melanomas in situ decreased from 38.96% to 16.98% in the year after the declaration of the state of alarm in Spain. Conclusions: The SARS-CoV-2 outbreak has led to a reduction in the early diagnosis of melanoma, with an increase in invasive melanomas with poor prognosis histological factors. This could lead to an increase in melanoma-related mortality in the coming years in our environment

The Burden of Hidradenitis Suppurativa Signs and Symptoms in Quality of Life: Systematic Review and Meta-Analysis

Hidradenitis suppurativa (HS) is a chronic, recurrent and debilitating inflammatory skin disease of the hair follicle that usually presents as painful, deep-seated inflamed lesions in the apocrine gland-bearing areas of the body. HS patients suffer from uncomfortable signs and symptoms, such as pain, pruritus, malodour and suppuration, which may impair patients’ quality of life (QoL). Although HS patients frequently experience these signs and symptoms, they are only occasionally assessed by clinicians and, unexpectedly, the scientific evidence available is limited and heterogeneous. The aim of this study is to summarize the evidence regarding the impact of HS signs and symptoms on QoL to serve as a basis for future research and help clinicians to consider them in the daily care of HS patients. A systematic review and meta-analysis were conducted following PRISMA Guidelines. The following search algorithm was used: (hidradenitis or “acne inversa”) and (pain or itch or odour or malodour or suppuration or oozing or drainage) and (“quality of life”). The literature search identified 836 references, 17 of them met the eligible criteria and were included for analysis, representing 4929 HS patients. Mean age of the participants was 36.28 years and there was a predominance of female sex among study participants. The BMI of the population was in the range of over-weight and about two out five patients were active smokers. Studies included patients with mild to moderate HS, with a mean disease duration of 13.69 years. The HS signs and symptoms assessed were pain, pruritus, malodour and suppuration. Overall, the higher intensity of a sign or symptom correlated with poorer general QoL or specific QoL dimensions including sexual distress, anxiety, depression and sleep. The most frequently employed tool to assess QoL was the Dermatology Life Quality Index (DLQI). DLQI was used in 52.9% of the studies (9/17) with a mean value of 10.70 (2.16 SD). The scores employed to assess signs and symptoms severity were subjective and varied between studies, being the numerical rating scale (NRS) for each of the most used symptoms. The mean NRS value for pain was 3.99 and the mean NRS for pruritus was 4.99. In conclusion, we have summarized, categorized and analyzed the scientific evidence regarding signs and symptoms in HS patients and their impairment in QoL. Their assessment should be thorough and included during routine evaluation of HS patients to motivate therapeutic modifications and increase patients’ health

Epidermal Barrier Function and Skin Homeostasis in Atopic Dermatitis: The Impact of Age

We would like to thank all the individuals who generously shared their time to participate in this research. The results of this study are part of the PhD work of Trinidad Montero-Vilchez.Skin is damaged in atopic dermatitis (AD) patients. Age is also believed to have a negative effect on epidermal barrier function. The aim of this study was to investigate skin barrier function changes with age in AD patients. A cross-sectional study was conducted including 162 participants, 81 AD patients and 81 healthy volunteers. Skin barrier function parameters, such as transepidermal water loss (TEWL), erythema, temperature, stratum corneum hydration (SCH), pH, and elasticity, were evaluated. Healthy volunteers were evaluated on the volar forearm. AD patients were measured on two regions: on an eczematous lesion on the volar forearm and on a non-involved area 5 cm from the affected area. TEWL was lower on healthy skin than uninvolved AD skin (9.98 vs. 25.51 g center dot m(-2)center dot h(-1), p < 0.001) and AD eczematous lesions (9.98 vs. 28.38 g center dot m(-2)center dot h(-1), p < 0.001). SCH was lower on AD eczematous lesions than uninvolved AD skin (24.23 vs. 39.36 AU, p < 0.001) and healthy skin (24.23 vs. 44.36 AU, p < 0.001). Elasticity was lower on AD eczematous lesions than uninvolved AD skin (0.69 vs. 0.74, p = 0.038) and healthy skin (0.69 vs. 0.77, p = 0.014). A negative correlation was found between age and elasticity in all the population (r = -0.383, p < 0.001). This correlation was stronger in AD patients (r = -0.494, p < 0.001) than in controls (r = -0.266, p = 0.092). After conducting a linear regression model in AD patients adjusted by age, sex, and SCORing Atopic Dermatitis (SCORAD), it was found that elasticity was impaired by an increasing age (beta = -0.004, p < 0.001) and a higher SCORAD (beta = -0.003, p < 0.001). The skin barrier function is impaired by age and AD, reflected mainly in poor elasticity values in older AD patients

Nucleolar Structure and Function in Trypanosomatid Protozoa

The nucleolus is the conspicuous nuclear body where ribosomal RNA genes are transcribed by RNA polymerase I, pre-ribosomal RNA is processed, and ribosomal subunits are assembled. Other important functions have been attributed to the nucleolus over the years. Here we review the current knowledge about the structure and function of the nucleolus in the trypanosomatid parasites Trypanosoma brucei, Trypanosoma cruzi and Leishmania ssp., which represent one of the earliest branching lineages among the eukaryotes. These protozoan parasites present a single nucleolus that is preserved throughout the closed nuclear division, and that seems to lack fibrillar centers. Trypanosomatids possess a relatively low number of rRNA genes, which encode rRNA molecules that contain large expansion segments, including several that are trypanosomatid-specific. Notably, the large subunit rRNA (28S-type) is fragmented into two large and four small rRNA species. Hence, compared to other organisms, the rRNA primary transcript requires additional processing steps in trypanosomatids. Accordingly, this group of parasites contains the highest number ever reported of snoRNAs that participate in rRNA processing. The number of modified rRNA nucleotides in trypanosomatids is also higher than in other organisms. Regarding the structure and biogenesis of the ribosomes, recent cryo-electron microscopy analyses have revealed several trypanosomatid-specific features that are discussed here. Additional functions of the nucleolus in trypanosomatids are also reviewed

Nucleolar Division in the Promastigote Stage of Leishmania major Parasite: A Nop56 Point of View

Nucleogenesis is the cellular event responsible for the formation of the new nucleoli at the end of mitosis. This process depends on the synthesis and processing of ribosomal RNA (rRNA) and, in some eukaryotes, the transfer of nucleolar material contained in prenucleolar bodies (PNBs) to active transcription sites. The lack of a comprehensive description of the nucleolus throughout the cell cycle of the human pathogen Leishmania major prompted us to analyze the distribution of nucleolar protein 56 (Nop56) during interphase and mitosis in the promastigote stage of the parasite. By in silico analysis we show that the orthologue of Nop56 in L. major (LmNop56) contains the three characteristic Nop56 domains and that its predicted three-dimensional structure is also conserved. Fluorescence microscopy observations indicate that the nucleolar localization of LmNop56 is similar, but not identical, to that of the nucleolar protein Elp3b. Notably, unlike other nucleolar proteins, LmNop56 remains associated with the nucleolus in nonproliferative cells. Moreover, epifluorescent images indicate the preservation of the nucleolar structure throughout the closed nuclear division. Experiments performed with the related parasite Trypanosoma brucei show that nucleolar division is carried out by an analogous mechanism