Alzheimer's disease (AD; OMIM, 104300) is an age-related neurodegenerative disorder and the most common type of dementia (Querfurth and LaFerla, 2010; Scheltens et al., 2021). AD is characterized by a series of pathological features including deposition of extracellular β-amyloid (Aβ) plaques, intracellular neurofibrillary tangles formed by hyperphosphorylated tau, neuronal loss, profound microgliosis, and astrocytosis (Querfurth and LaFerla, 2010; De Strooper and Karran, 2016; Scheltens et al., 2021). Growth factors (GFs) are multifunctional proteins that affect the rate of cell proliferation, differentiation and migration, and also tissue remodeling and inflammation (Bottner et al., 2000; Rodrigues et al., 2010; Li et al., 2012; Seeger and Paller, 2015). There are several different kinds of GFs, including the transforming growth factor β (TGF-β) superfamily, fibroblast growth factors (FGFs), insulin derived growth factors (IGFs), epidermal growth factor (EGF) superfamily, vascular endothelial growth factor (VEGF) family, nerve growth factor (NGF) family, platelet-derived growth factor (PDGF) family, and so on. The GFs play important roles in neurogenesis, neurodegeneration (Woodbury and Ikezu, 2014), synapse formation (Schmeisser et al., 2012), axonal transport (Schindowski et al., 2008), and homeostasis of the central nervous system (CNS) (Bottner et al., 2000; Lauzon et al., 2015). The changes of GF levels in blood plasma (Mocali et al., 2004; Ray et al., 2007; Johansson et al., 2013) and brain of AD patients (Rivera et al., 2005; Mahoney et al., 2021) have been reported frequently, and they may be associated with the cognitive or clinical outcomes of AD (Ray et al., 2007; Hohman et al., 2015; Lim et al., 2016). The signaling pathways of GFs have also been demonstrated to be involved in the pathogenesis of AD (Patel et al., 2010; Turner et al., 2016). These signaling abnormalities in turn may impair synaptic plasticity and cognition in AD progression (Caraci et al., 2015; Ferreira, 2021). Due to their functional importance and the advances in recent studies, the targeting of GFs may offer considerable therapeutic potential in the treatment of AD (Freiherr et al., 2013; Lauzon et al., 2015).

AD is a highly heritable disease with population heterogeneity (Lambert and Amouyel, 2007; McClellan and King, 2010). The heritability of AD ranges from 58% to 79% (Gatz et al., 2006). Apart from biomarker evaluation and functional characterizations, genetic studies have also indicated the contributions and involvement of GFs in AD. Several genetic association studies focusing on limited numbers of variants and candidate genes have identified association of some GFs with AD (Luedecking et al., 2000; Chapuis et al., 2006; Wang et al., 2012; Yang et al., 2016). However, the conclusions in these studies have been somewhat controversial, partially because of their relatively small sample size and population substructure (Chang et al., 2013; Liu et al., 2013). In recent genomic studies with large sample size of European populations or populations of European ancestry, one of the growth factors, EGFR, was highlighted as a potentially causal gene by gene prioritization and knockoff-based methods (He et al., 2021; Bellenguez et al., 2022). Genomic studies of AD in Chinese (Wang et al., 2018a; Zhou et al., 2018; Zhang et al., 2019; Jia et al., 2021) and Japanese and Korean populations (Miyashita et al., 2013; Shigemizu et al., 2021) have emerged in recent years, and reported several risk genes, although again the studies have been limited by relatively small sample sizes. Considering the fact that GFs have been found to be actively involved in AD, it is appropriate to perform a comprehensive analysis of GF variants in Han Chinese with AD.

In this study, we performed a 3-stage study combining targeted next-generation sequencing (NGS) and meta-analysis in 1280 AD patients and 5044 normal control subjects from the Han Chinese population. We successfully sequenced the exon and nearby untranslated regions (UTRs) of 23 GFs and examined the association of common (minor allele frequency (MAF) ≥ 0.01 in control samples) and rare variants (MAF < 0.01) with AD. We identified a novel AD risk gene EGF, with both its common and rare variants being associated with AD in Han Chinese.