Prion diseases are incurable neurodegenerative disorders in which the normal cellular prion protein (PrPC) converts into a misfolded isoform (PrPSc) with unique biochemical and structural properties that correlate with disease. In humans, prion disorders, such as Creutzfeldt-Jakob disease, present typically with a sporadic origin, where unknown mechanisms lead to the spontaneous misfolding and deposition of wild type PrP. To shed light on how wild-type PrP undergoes conformational changes and which are the cellular components involved in this process, we analyzed the dynamics of wild-type PrP from hamster in transgenic flies. In young flies, PrP demonstrates properties of the benign PrPC; in older flies, PrP misfolds, acquires biochemical and structural properties of PrPSc, and induces spongiform degeneration of brain neurons. Aged flies accumulate insoluble PrP that resists high concentrations of denaturing agents and contains PrPSc-specific conformational epitopes. In contrast to PrPSc from mammals, PrP is proteinase-sensitive in flies. Thus, wild-type PrP rapidly converts in vivo into a neurotoxic, protease-sensitive isoform distinct from prototypical PrPSc. Next, we investigated the role of molecular chaperones in PrP misfolding in vivo. Remarkably, Hsp70 prevents the accumulation of PrPSc-like conformers and protects against PrP-dependent neurodegeneration. This protective activity involves the direct interaction between Hsp70 and PrP, which may occur in active membrane microdomains such as lipid rafts, where we detected Hsp70. These results highlight the ability of wild-type PrP to spontaneously convert in vivo into a protease-sensitive isoform that is neurotoxic, supporting the idea that protease-resistant PrPSc is not required for pathology. Moreover, we identify a new role for Hsp70 in the accumulation of misfolded PrP. Overall, we provide new insight into the mechanisms of spontaneous accumulation of neurotoxic PrP and uncover the potential therapeutic role of Hsp70 in treating these devastating disorders.

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Alopecia areata (AA) is a skin condition in which hair is lost from certain or all areas of the body. This condition has been described as an immune-mediated complex genetic disease, characterized by the presence of lymphocytes that are directed to the hair follicles in the anagen phase. The gene encoding the protein tyrosine phosphatase, non-receptor type 22 (PTPN22), which is exclusively expressed in immune cells, has been considered as a risk factor associated with a number of autoimmune diseases. In AA, the single nucleotide polymorphism, rs2476601, has been identified as a risk factor in several populations. The aim of the present study was to investigate the effect of PTPN22 C1858T inherited genetic polymorphism on the predisposition to severe forms of AA, in a case-control study on individuals. The study included 64 unrelated patients diagnosed with several types of AA, as well as 225 healthy unrelated subjects. The DNA samples were genotyped for PTPN22 C1858T polymorphism using the polymerase chain reaction-restriction fragment length polymorphism technique. Causal associations were determined by χ test and their respective odds ratio (OR) was assessed in a 2×2 contingency table. The results demonstrated a significant association of the T allele [P=0.040; OR=3.196; 95% confidence interval (CI), 0.094-10.279] and the CT genotype (P=0.038; OR=3.313; 95% CI, 1.008-10.892) with patchy AA. In conclusion, the results of the present study suggested the possible involvement of the T allele of the PTPN22 C1858T SNP as a genetic risk factor for this type of AA in the population studied.

Diabetic retinopathy (DR) is one of the primary causes of blindness in the working age population and is characterized by angiogenesis in the retina. Platelets have been suggested to be involved in the pathogenesis of diabetic microvascular complications. The integrin receptor for collagen/laminin, α2β1, mediates platelet primary adhesion to subendothelial tissues, which is an essential first step in thrombus formation. The gene encoding the α2 subunit of α2β1 integrin has ≥8 polymorphisms, including a BglII/NdeI restriction fragment length polymorphism. To explore the prevalence of DR in a population from Northeastern Mexico, unrelated, hospitalized patients who had received a diagnosis of type 2 diabetes mellitus (DM2) at least 10 years previously were recruited (n=177). DR was diagnosed in a masked manner by independent ophthalmologists using fundus images captured using a non-mydriatic retinal camera. A total of 121 patients with DM2 (68%) had some degree of DR development (DR patients), and 56 patients with DM2 (32%) did not exhibit any sign of DR (No-DR patients). The results showed that after 15 years of DM2 progression, there is an increased risk of DR (P=0.0497; odds ratio, 1.993). In addition, insulin therapy and family history of DM2 were significantly associated with DR. In order to detect a possible association between DR and BglII/NdeI α2 gene polymorphisms, a comparative cross-sectional study between DR and No-DR patients was conducted. The α2 gene was genotyped by polymerase chain reaction-restriction fragment length polymorphism assay. Statistical analysis revealed no association between BglII/NdeI genotypes and the development of DR in this group of patients. In conclusion, the present data indicate a high prevalence of DR in the Mexican population and suggest that the damage in DR is due to other factors, such as the duration of the DM2, and is not linked to BglII/NdeI α2 gene polymorphisms.

We have addressed the control of longitudinal axon pathfinding in the developing hindbrain, including the caudal projections of reticular and raphe neurons. To test potential sources of guidance signals, we assessed axon outgrowth from embryonic rat hindbrain explants cultured in collagen gels at a distance from explants of midbrain-hindbrain boundary (isthmus), caudal hindbrain, or cervical spinal cord. Our results showed that the isthmus inhibited caudally directed axon outgrowth by 80% relative to controls, whereas rostrally directed axon outgrowth was unaffected. Moreover, caudal hindbrain or cervical spinal cord explants did not inhibit caudal axons. Immunohistochemistry for reticular and raphe neuronal markers indicated that the caudal, but not the rostral projections of these neuronal subpopulations were inhibited by isthmic explants. Companion studies in chick embryos showed that, when the hindbrain was surgically separated from the isthmus, caudal reticulospinal axon projections failed to form and that descending pioneer axons of the medial longitudinal fasciculus (MLF) play an important role in the caudal reticulospinal projection. Taken together, these results suggest that diffusible chemorepellent or nonpermissive signals from the isthmus and substrate-anchored signals on the pioneer MLF axons are involved in the caudal direction of reticulospinal projections and might influence other longitudinal axon projections in the brainstem.