## 4 Materials and Methods
### Microarray-Based Assay for SNP Genotyping and Calculation of the PRS  
In this study, we examined a panel of SNPs that were included in the PRS model proposed by [PERSON] et al. for AD [9]. The panel included the following SNPs: rs6656401 in the _CR1_ gene; rs6733839 in the _BIN1_ gene; rs35349669 in the _INPP5D_ gene; rs190982 in the _MEF2C_ gene; rs9271192 in the _HLA-DRB5/1_ gene; rs10948363 in the _CD2 AP_ gene; rs271 8058 in the _NME8_ gene; rs1476679 in the _ZCWPW1_ gene; rs11771145 in the _EPHA1_ gene; rs28834970 in the _PTK2B_ gene; rs9331896 in the _CLU_ gene; rs10838725 in the _CLF1_ gene; rs7274581 in the _CAS54_ gene; rs983392 in the _MS4A6A_ gene; rs10792832 in the _PICALM_ gene; rs112 18,343 in the _SORL1_ gene; rs17125944 in the _FERMT2_ gene; rs10498633 in the _RIN-SLC24A_ gene; rs8093731 in the _DSG2_ gene; rs4147929 in the _ABCA7_ gene; and rs386544 in the _CD33_ gene (if the SNP is located in the intergenic region, the closest gene is indicated). Simultaneously, we analyzed rs429358 and rs7412, which determine the \(\epsilon\) alleles of the _APOE_ gene. The identification of 23 SNPs was carried out using a molecular technique that utilizes hydrogel-based oligonucleotide microarray technology developed at the Engelhardt Institute of Molecular Biology, Russian Academy of Sciences [31]. The microarray consisted of a plastic substrate with hydrogel elements (droplets) that were deposited and contained immobilized oligonucleotides. The process of designing and synthesizing oligonucleotides for immobilization, along with the manufacture of microarrays using a copolymerization \begin{table}
\begin{tabular}{c c c} \hline  & **CN Volunteers** & **Dementia** \\ \hline Sex, female & 71.48\% (371/519) & 65.71\% (228/347) \\ \hline Higher education & 57.14\% (52/91) & 31.06\% (91/293) \\ \hline Family & 63.16\% (60/95) & 46.69\% (141/302) \\ \hline Children & 100\% (82/82) & 55\% (165/300) \\ \hline Intellectual Work & 82.6\% (76/92) & 46.6\% (124/266) \\ \hline Age, mean (sd, min–max) & 71.42 (7.19, 59–94) & 73.09 (11.4, 35–97) \\ \hline MMSE, mean (sd, min–max) & 28.84 (0.72, 28–30) & 9.97 (6.5, 0–24) \\ \hline CDT mean (sd, min–max) & 7.31 (2.82, 1–10) & 3.81 (2.93, 0–10) \\ \hline MoCA mean (sd, min–max) & 24.93 (2.71, 18–30) & 9.14 (5, 0–22) \\ \hline \end{tabular}
\end{table} 
Table 4: Characteristics of dementia patients and CN volunteers. immobilization method, follows the previously described protocol [38]. Supplementary File S1 provides the sequences of the immobilized probes. Figure 4a displays the layout of the microarray that holds oligonucleotides for identifying 23 SNPs. The assay protocol involved multiplex PCR to generate mostly single-stranded, fluorescence-labeled DNA fragments, followed by the hybridization of the DNA fragments on a microarray and the acquisition and analysis of fluorescence images. The primer sequences em  
Figure 4: DNA hydrogel microarray for genotyping SNPs associated with Alzheimer’s disease. (**a**) Configuration of the microarray. The analyzed SNPs are indicated within the circles, representing the microarray elements. The microarray included 92 hydrogel elements containing immobilized oligonucleotide probes, two marker elements (M) for image acquisition and processing software, and four empty hydrogel elements for signal normalization. The microarray elements were categorized into 23 groups denoted by distinct colors, which correspond to the analyzed SNPs. Each group comprises four elements, with two of them containing oligonucleotides that match the wild-type allele, while the other two hold probes that correspond to the minor allele. The microarray elements were duplicated to ensure reliable analysis. The right column lists the SNPs and their relevant genes. (**b**) Fluorescence hybridization pattern of the microarray following analysis of genomic DNA from a patient with Alzheimer’s disease. The genotypes obtained for each SNP, PRS, and _APOE_ genotype are displayed in the right column.