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. 2023 Mar;44(3):919-930.
doi: 10.1007/s10072-022-06500-2. Epub 2022 Nov 17.

RNAseq analysis of olfactory neuroepithelium cytological samples in individuals with Down syndrome compared to euploid controls: a pilot study

Lorenzo Brozzetti #  1 , Ilaria Scambi #  2 , Loris Bertoldi #  3 , Alice Zanini  2 , Giorgio Malacrida  3 , Luca Sacchetto  4 , Lucia Baldassa  5 , Giuseppe Benvenuto  3 , Raffaella Mariotti  2 , Gianluigi Zanusso  1 , Maria Paola Cecchini  6
Affiliations

RNAseq analysis of olfactory neuroepithelium cytological samples in individuals with Down syndrome compared to euploid controls: a pilot study

Lorenzo Brozzetti et al. Neurol Sci. 2023 Mar.

Abstract

Down syndrome is a common genetic disorder caused by partial or complete triplication of chromosome 21. This syndrome shows an overall and progressive impairment of olfactory function, detected early in adulthood. The olfactory neuronal cells are located in the nasal olfactory mucosa and represent the first sensory neurons of the olfactory pathway. Herein, we applied the olfactory swabbing procedure to allow a gentle collection of olfactory epithelial cells in seven individuals with Down syndrome and in ten euploid controls. The aim of this research was to investigate the peripheral gene expression pattern in olfactory epithelial cells through RNAseq analysis. Validated tests (Sniffin' Sticks Extended test) were used to assess olfactory function. Olfactory scores were correlated with RNAseq results and cognitive scores (Vineland II and Leiter scales). All Down syndrome individuals showed both olfactory deficit and intellectual disability. Down syndrome individuals and euploid controls exhibited clear expression differences in genes located in and outside the chromosome 21. In addition, a significant correlation was found between olfactory test scores and gene expression, while a non-significant correlation emerged between olfactory and cognitive scores. This first preliminary step gives new insights into the Down syndrome olfactory system research, starting from the olfactory neuroepithelium, the first cellular step on the olfactory way.

Keywords: Differential gene expression analysis; Down syndrome; Euploid controls; Olfactory neuroepithelium swabbing; RNAseq analysis.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Down syndrome DEG heatmap. Cluster heatmap shows samples in columns and genes in rows. The level of expression is represented by the background color, where blue means low and red means high expression. Experimental conditions are shown in green and purple, illustrating euploid controls and Down syndrome (DS) individuals respectively
Fig. 2
Fig. 2
DEG and olfactory scores correlation matrix. Pearson’s coefficient (lower triangle) and p-value (upper triangle) between the expression of interesting differentially expressed genes in Down syndrome (DS) individuals (upregulated: MUC16, CREB5, CREB3L2, DYRK1A, DOPEYE2, APP, POFUT2, S100PBP; downregulated: PAX7, KLF9, SPARCL1, ITGA6, STATH) and olfactory test scores (TDI, T, D, I) are shown in the matrix. Blue background indicates negative correlation while red indicates positive. p-value background ranges from pale yellow (high significance) to green (no significance). T, threshold; D, discrimination; I, identification; TDI, total smell score
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