Analysis of newly detected mutations in the MCFD2 gene giving rise to combined deficiency of coagulation factors V and VIII

The use of pharmacological chaperones in rare diseases caused by reduced protein stability

Rare diseases are most often caused by inherited genetic disorders that, after translation, will result in a protein with altered function. Decreased protein stability is the most frequent mechanism associated with a congenital pathogenic missense mutation and it implies the destabilization of the folded conformation in favour of unfolded or misfolded states. In the cellular context and when experimental data is available, a mutant protein with altered thermodynamic stability often also results in impaired homeostasis, with the deleterious accumulation of protein aggregates, metabolites and/or metabolic by-products. In the last decades, a significant effort has enabled the characterization of rare diseases associated to protein stability defects and triggered the development of innovative therapeutic intervention lines, say, the use of pharmacological chaperones to correct the intracellular impaired homeostasis. Here, we review the current knowledge on rare diseases caused by reduced protein stability, paying special attention to the thermodynamic aspects of the protein destabilization, also focusing on some examples where pharmacological chaperones are being tested.

The Glanzmann's Thrombasthenia in Tunisia: A Cohort Study

Background

The Glanzmann’s thrombasthenia (GT) is a rare autosomal-recessive bleeding disorder with uncommon neonatal revelation. It is due to abnormalities of quantitative and/or qualitative α_IIbβ₃ integrin. This cell adhesion receptor is essential for platelet aggregation and allows the formation of a hemostatic plug if the vessel is damaged by injury. The clinical picture of GT is variable, with mucocutaneous bleeding due to non-functional platelets. Management requires a good expertise in bleeding disorders. We describe the clinical and the epidemiological data of GT in Aziza Othmana Hospital Hemophilia Center.

Methods

This was a retrospective study of all patients with GT monitored and treated in our hemophilia center during the period of 2011 - 2015.

Results

Twenty-seven patients among the 35 patients included in our hemophilia center registry were studied. The most common sign encountered is the gingival bleeding. In our women cohort, one completed her pregnancy. The consanguinity is present with a frequency of 62%. Treatments used depending on the case are tranexamic acid, platelet transfusion, packed red blood cells and rFVIIa, respectively.

Conclusion

GT is relatively frequent in Tunisia and especially in the North of the country which can be explained by the high consanguinity in our population.

Global analyses of Chromosome 17 and 18 genes of lung telocytes compared with mesenchymal stem cells, fibroblasts, alveolar type II cells, airway epithelial cells, and lymphocytes

Background

Telocytes (TCs) is an interstitial cell with extremely long and thin telopodes (Tps) with thin segments (podomers) and dilations (podoms) to interact with neighboring cells. TCs have been found in different organs, while there is still a lack of TCs-specific biomarkers to distinguish TCs from the other cells.

Results

We compared gene expression profiles of murine pulmonary TCs on days 5 (TC5) and days 10 (TC10) with mesenchymal stem cells (MSCs), fibroblasts (Fbs), alveolar type II cells (ATII), airway basal cells (ABCs), proximal airway cells (PACs), CD8⁺ T cells from bronchial lymph nodes (T-BL), and CD8⁺ T cells from lungs (T-LL). The chromosome 17 and 18 genes were extracted for further analysis. The TCs-specific genes and functional networks were identified and analyzed by bioinformatics tools. 16 and 10 of TCs-specific genes were up-regulated and 68 and 22 were down-regulated in chromosome 17 and 18, as compared with other cells respectively. Of them, Mapk14 and Trem2 were up-regulated to indicate the biological function of TCs in immune regulation, and up-regulated MCFD2 and down-regulated E4F1 and PDCD2 had an association with tissue homeostasis for TCs. Over-expressed Dpysl3 may promote TCs self-proliferation and cell-cell network forming.

Conclusions

The differential gene expression in chromosomes 17 and 18 clearly revealed that TCs were the distinctive type of interstitial cells. Our data also indicates that TCs may play a dual role in immune surveillance and immune homoeostasis to keep from immune disorder in acute and chronic pulmonary diseases. TCs also participated in proliferation, differentiation and regeneration.

Reviewers

This article was reviewed by Qing Kay Li and Dragos Cretoiu.

Electronic supplementary material

The online version of this article (doi:10.1186/s13062-015-0042-0) contains supplementary material, which is available to authorized users.

Combined deficiency of coagulation factors V and VIII: an update

Combined deficiency of factor V (FV) and FVIII (F5F8D) is an autosomal recessive bleeding disorder characterized by simultaneous decreases of both coagulation factors. This review summarizes recent reports on the clinical presentations, treatments, and molecular mechanism of F5F8D. Genetic studies identified LMAN1 and MCFD2 as causative genes for this disorder, revealing a previously unknown intracellular transport pathway shared by the two important blood coagulation factors. LMAN1 and MCFD2 form a Ca2+-dependent cargo receptor complex that functions in the transport of FV/FVIII from the endoplasmic reticulum (ER) to the Golgi. Disrupting the LMAN1-MCFD2 receptor, complex formation is the primary molecular defect of missense mutations leading to F5F8D. The EF-hand domains of MCFD2 are necessary and sufficient for the interactions with both LMAN1 and FV/FVIII. Similarly, the carbohydrate recognition domain of LMAN1 contains distinct and separable binding sites for both MCFD2 and FV/FVIII. Therefore, FV and FVIII likely carry duel sorting signals that are separately recognized by LMAN1 and MCFD2 and necessary for the efficient ER-to-Golgi transport. FV and FVIII likely bind LMAN1 through the high-mannose N-linked glycans under the higher Ca2+ conditions in the ER and dissociate in the lower Ca2+ environment of the ER-Golgi intermediate compartment.