Diploma thesis title: Cutaneous innervation of St8sia1 knockout mice Objectives: The aim of this study was to investigate whether the knock out of the St8sia1 gene will affect peripheral innervation of mouse ear skin and the density of different types of nerve fibers since mutations in the St8sia1 gene are associated with neurodegenerative processes. Materials and methods: Thirteen six-month-old mice were used in the study, eight of them were St8sia1-knock out mice and five of them were control-type wild-type mice (C57BL / 6 strain). After euthanasia, mouse ear tissue was taken and then embedded in paraffin blocks. Obtained histological preparations were stained immunohistochemically according to standard procedures. The primary antibodies used were Anti-NF52, Anti-CGRP, Anti-TH and Anti-ChAT. After incubation with the primary antibodies, the samples were washed with PBS and after being washed out the samples were incubated for one hour with the secondary antibodies. Secondary antibodies that were used are Donkey Anti-Rabbit IgG, Alexa Fluor® 488 and Donkey Anti-Sheep IgG H + L Alexa Fluor® 488. Histological preparations were examined with a BX51 Olympus microscope equipped with a cooled digital camera and photographs were taken for further analysis. The microphotographs were further analyzed in Adobe Photoshop CS2 and the areas of interest were the skin and subcutaneous tissue of the mouse ear. The results were statistically processed in GraphPad Prism 8.0.1. program and for a statistically significant difference was set the value of P <0,05. Results: Analysis of the percentage of N52 surface area of immunoreactive nerve fibers has shown a statistically significant difference in the reduced innervation density of mouse skin comparing WT and KO groups (P = 0,049). Likewise, the density of ChAT-immunoreactive nerve fibers was reduced in the St8sia1 knock out mice (P = 0,035). Unlike the previous one, no significant difference was found in the density of sympathetic innervation of the skin (TH marker) and subcutaneous tissue between wild-type mice and St8sia1 knock out mice (P = 0,122). Furthermore, the density of innervation by peptidergic CGRP immunoreactive nerve fibers did not differ between the two studied strains (P = 0,349). Conclusions: Knock-out of the St8sia1 gene in mice results in a disturbance of peripheral innervation, which is manifested by a decrease in the density of peripheral nerve fibers in the skin. Peripheral innervation disorder has a selective effect only on myelinated nerve fibers, while unmyelinated neurons were not affected.