Medical Genetic Study of Hereditary Diseases in Abazins of the Karachay-Cherkess Republic

This paper estimates the load and nosological spectrum of monogenic hereditary diseases (HDs) in Abazins of the Karachay-Cherkess Republic (KChR), identified in Cherkessk and ten districts, Abazinsky, Ust-Dzhegutinsky, Malokarachaevsky, Karachaevsky, Prikubansky, Khabezsky, Nogaysky, Adyge-Khablsky, Urupsky, and Zelenchuksky. The number of the investigated population was 387231 individuals (including 33264 Abazins). We detected 153 patients from 105 families with 45 nosological forms of HDs: 83 patients from 50 families with 23 AD diseases, 47 patients from 42 families with 15 AR diseases, and 23 patients from 13 families with 7 X-linked diseases. The total load of HDs in Abazins was 1: 218 individuals (in the rural population 1: 162, in the urban population 1: 305). Frequent and rare nosological forms of HDs and the accumulation of certain diseases in Abazins in comparison with the previously surveyed populations of Russia were determined. On the basis of the prevalence of AD and AR hereditary diseases, a principal component analysis was carried out, which determined the genogeographical position of Abazins among nine ethnic groups (13 populations) of Russian Federation: six Russian regions, Bashkirs of the Bashkortostan, Tatars of the Tatarstan, Chuvashes of the Chuvashia, Maris of the Mari El, Udmurts of the Udmurtia, Adygeans of the Adygea, and Circassians and Abazins of the KChR.     

Hereditary deafness in Kirov oblast: A genetic epidemiological study

The results of a genetic epidemiological study of hereditary deafness (HD) in ten raions (districts) of Kirov oblast (administrative region), Russia, are presented. A total of 122 075 people have been examined. Segregation analysis of all families with diagnosed HD has demonstrated a good fit to either the autosomal dominant (AD) or autosomal recessive (AR) mode of inheritance. The total prevalence rates of AD and AR HDs, as well as the specific prevalence rates of nonsyndromic and syndromic forms of HD, have been calculated for the population of ten raions. The HD prevalence rate in Kirov oblast has been found to be 1: 1043 people (1: 1453 and 1: 3699 for the nonsyndromic and syndromic forms, respectively). This value has been found to vary in different raions, which is explained by differences in the genetic subdivision levels of the populations studied; the correlation coefficient between the HD load and random inbreeding (F _ST) in district populations is r = 0.81 ± 0.22. The diversity of syndromic hearing disorders is described.     

Three novel and two known androgen receptor gene mutations associated with androgen insensitivity syndrome in sex-reversed XY female patients

Molecular characterization of 23 cytogenetically confirmed XY females was attempted by screening coding regions of SRY and androgen receptor (AR) genes. Five of the index cases showed sequence variations in various exons of the AR gene: a deletion (n.1911delG) and substitutions n.1761G >A and n.1317C >T in exon 1; n.3510C >T transition in exon 6 and deletion mutation (n.3672delT) in exon 7. Four mutations identified here lead to the formation of truncated receptor protein, involving a substantial loss of AR functional domains which explains the phenotype in the subjects. The n.1761G >A substitution has been previously reported in cases with mild androgen insensitivity. Although the ligand-binding domain was considered as the mutational hot spot in AR gene, we report here 3/5 variations in the N-terminal domain emphasizing the significance of considering the N-terminal domain of AR as well for mutation screening. Our present observation also strengthens the role of AR gene and its direct association with AIS.     

Hereditary deafness in Kirov oblast: a genetic epidemiological study

The results of a genetic epidemiological study of hereditary deafness (HD) in ten raions (districts) of Kirov oblast (administrative region), Russia, are presented. A total of 122 075 people have been examined. Segregation analysis of all families with diagnosed HD has demonstrated a good fit to either the autosomal dominant (AD) or autosomal recessive (AR) mode of inheritance. The total prevalence rates of AD and AR HDs, as well as the specific prevalence rates of nonsyndromic and syndromic forms of HD, have been calculated for the population often raions. The HD prevalence rate in Kirov oblast has been found to be 1 : 1043 people (1 : 1453 and 1 : 3699 for the nonsyndromic and syndromic forms, respectively). This value has been found to vary in different raions, which is explained by differences in the genetic subdivision levels of the populations studied; the correlation coefficient between the HD load and random inbreeding (F(ST)) in district populations is r = 0.81 +/- 0.22. The diversity of syndromic hearing disorders is described.     

Genetic Association of <Emphasis Type="Italic">HLA</Emphasis> Gene Variants with MRI Brain Structure in Alzheimer’s Disease

There is accumulating evidence that the human leukocyte antigen (HLA) gene variants are associated with Alzheimer’s disease (AD). However, how they affect AD occurrence is still unknown. In this study, we firstly investigated the association of gene variants in HLA gene variants and brain structures on MRI in a large sample from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) to explore the effects of HLA on AD pathogenesis. We selected hippocampus, hippocampus CA1 subregion, parahippocampus, posterior cingulate, precuneus, middle temporal, entorhinal cortex, and amygdala as regions of interest (ROIs). According to the previous association studies of HLA variants and AD, 12 SNPs in HLA were identified in the dataset following quality control measures. In total group analysis, our results showed that TNF-α SNPs at rs2534672 and rs2395488 were significantly positively associated with the volume of the left middle temporal lobe (rs2534672: P?=?0.00035, Pc?=?0.004; rs2395488: P?=?0.0038, Pc?=?0.023) at baseline. In the longitudinal study, HFE rs1800562 was remarkably correlated with the lower atrophy rate of right middle temporal lobe (P?=?0.0003, Pc?=?0.003) and RAGE rs2070600 was associated with the atrophy rate of right hippocampus substructure-CA1 over 2 years (P?=?0.003, Pc?=?0.035). Furthermore, we detected the above four associations in mild cognitive impairment (MCI) subgroup analysis, as well as the association of rs2534672 with the baseline volume of the left middle temporal lobe in normal cognition (NC) subgroup analysis. Our study provided preliminary evidences that HLA gene variants might participate in the structural alteration of AD associated brain regions, hence modulating the susceptibility of AD.     

A novel co-culture system of adventitious roots of <Emphasis Type="Italic">Echinacea</Emphasis> species in bioreactors for high production of bioactive compounds

To efficiently produce bioactive compounds of Echinacea via adventitious root (AR) culture, we established an AR co-culture system of Echinacea species. ARs of different combination of Echinacea species [E. pallida (Epa), E. purpurea (Epu), and E. angustifolia (Ean)] were inoculated into 5 L balloon-type airlift bioreactors to select a suitable combination group. The biomass of ARs increased in the Epa+Epu group but decreased in co-culture groups of Epa+Ean and Epa+Epu+Ean. In the Epa+Epu group, the content and productivity of total phenolics, flavonoids, and caffeic acid derivatives increased, a monomer of caffeic acid derivatives (caffeic acid) that is absent in single-species cultures (Epa or Epu) were synthesized; moreover, Epa+Epu also showed the highest antioxidant activity. The inoculum proportions in Epa+Epu significantly influenced the co-culture effect; among the proportion groups (Epa:Epu?=?1:6, 2:5, 3:4, 1:1, 4:4, 5:2, and 6:1), the Epa:Epu proportion of 4:3 was the most favorable for AR biomass and bioactive compound accumulation, and the antioxidant activity also peaked at 4:3 proportion. In addition, the co-culture system is suitable for large bioreactors (10 and 20 L), wherein the AR biomass increased without a decrease in the amount of bioactive compounds. A co-culture system was thus successfully established in this study, and AR cultures are expected to be used as an alternative raw material for the production of Echinacea-derived products.     

Associations of polymorphisms in the candidate genes for Alzheimer’s disease <Emphasis Type="Italic">BIN1, CLU,CR1</Emphasis> and <Emphasis Type="Italic">PICALM</Emphasis> with gestational diabetes and impaired glucose tolerance

Alzheimer’s disease (AD) is the most common type of dementia, with a prevalence that is rising every year. AD is associated with type 2 diabetes mellitus (T2DM) and insulin resistance, and is therefore sometimes called “type 3 diabetes mellitus”. The aim of this study was to examine whether the variants of some candidate genes involved in the development of AD, namely BIN1 (rs744373), CLU (rs11136000), CR1 (rs3818361), and PICALM (rs3851179), are related to several disorders of glucose metabolism—gestational diabetes (GDM), T2DM and impaired glucose tolerance (IGT). Our study included 550 women with former GDM and 717 control women, 392 patients with T2DM and 180 non-diabetic controls, and 117 patients with IGT and 630 controls with normal glucose tolerance. Genotyping analysis was performed using specially-designed TaqMan assays. No significant associations of the genetic variants rs744373 in BIN1, rs11136000 in CLU, or rs3818361 in CR1 were found with GDM, T2DM or IGT, but rs3851179 in PICALM was associated with an increased risk of GDM. The frequency of the AD risk-associated C allele was significantly higher in the GDM group compared to controls: OR 1.21; 95% CI (1.03–1.44). This finding was not apparent in T2DM and IGT; conversely, the C allele of the PICALM SNP was protective for IGT: OR 0.67; 95% CI (0.51–0.89). This study demonstrates an association between PICALM rs3851179 and GDM as well as IGT. However, elucidation of the possible role of this gene in the pathogenesis of GDM requires further independent studies.     

Overexpression of cytochrome p450 125 in <Emphasis Type="Italic">Mycobacterium</Emphasis>: a rational strategy in the promotion of phytosterol biotransformation

Androst-4-ene-3, 17-dione (AD) and androst-1, 4-diene-3, 17-dione (ADD) are generally produced by the biotransformation of phytosterols in Mycobacterium. The AD (D) production increases when the strain has high NAD⁺/NADH ratio. To enhance the AD (D) production in Mycobacterium neoaurum TCCC 11978 (MNR M3), a rational strategy was developed through overexpression of a gene involved in the phytosterol degradation pathway; NAD⁺ was generated as well. Proteomic analysis of MNR cultured with and without phytosterols showed that the steroid C27-monooxygenase (Cyp125-3), which performs sequential oxidations of the sterol side chain at the C27 position and has the oxidative cofactor of NAD⁺ generated, played an important role in the phytosterol biotransformation process of MNR M3. To improve the productivity of AD (D), the cyp125-3 gene was overexpressed in MNR M3. The specific activity of Cyp125-3 in the recombinant strain MNR M3C3 was improved by 22% than that in MNR M3. The NAD⁺/NADH ratio in MNR M3C3 was 131% higher than that in the parent strain. During phytosterol biotransformation, the conversion of sterols increased from 84 to 96%, and the yield of AD (D) by MNR M3C3 was increased by approximately 18% for 96 h fermentation. This rational strain modification strategy may also be applied to develop strains with important application values for efficient production of cofactor-dependent metabolites.     

Anti-cancer labdane diterpenoids from adventitious roots of <Emphasis Type="Italic">Andrographis paniculata</Emphasis>: augmentation of production prospect endowed with pathway gene expression

Andrographolide (AD) is the time-honoured pharmacologically active constituent of the traditionally renowned medicinal plant—Andrographis paniculata. Advancements in the target-oriented drug discovery process have further unravelled the immense therapeutic credibility of another unique molecule—neoandrographolide (NAD). The escalated market demand of these anti-cancer diterpenes is increasingly facing unrelenting hurdles of demand and supply disparity, attributable to their limited yield. Callus and adventitious root cultures were generated to explore their biosynthetic potentials which first time revealed NAD production along with AD. Optimization of the types and concentrations of auxins along with media form and cultivation time led to the successful tuning towards establishing adventitious roots as a superior production alternative for both AD/NAD. Supplementation of IBA to the NAA + Kn-containing MS medium boosted the overall growth and AD/NAD synthesis in the adventitious roots. Compared to control leaves, the adventitious root exhibited about 2.61- and 8.8-fold higher contents of AD and NAD, respectively. The qRT-PCR involving nine key pathway genes was studied, which revealed upregulation of GGPS1 and HMGR1/2 genes and downregulation of DXS1/2 and HDR1/2 genes in the adventitious root as compared to that in the control leaves. Such observations highlight that in vitro cultures can serve as efficient production alternatives for AD/NAD as the cytosolic genes (HMGR1/2 of MVA pathway) are competent enough to take over from the plastidial genes (DXS1/2 and HDR1/2 of MEP pathway), provided the accredited first branch-point regulatory gene (GGPS) expression and the culture requirements are optimally fulfilled.     

Results of molecular genetic testing in Russian patients with Pendred syndrome and allelic disorders

Pendred syndrome is an autosomal recessive inherited disorder characterized by a combination of sensorineural hearing impairment and euthyroid goiter; its clinical manifestation in children is hardly distinguishable from nonsyndromic hearing loss. Pendred syndrome is one of the most frequent types of syndromic hearing loss. Hearing impairment is accompanied by abnormal development of the bony labyrinth—enlarged vestibular aqueduct (EVA) and occasionally combined with Mondini dysplasia. Mutations in the SLC26A4 gene, which encodes the pendrin protein, are responsible for both Pendred syndrome and for allelic disorder (nonsyndromic enlarged vestibular aqueduct). The present study for the first time conducted molecular genetic analysis in 20 Russian patients with Pendred syndrome, EVA and/or Mondini dysplasia. As a result, six pathogenic mutations in the SLC26A4 gene were revealed in four patients. The mutation c.222G>T (p.Trp74Cys) was detected for the first time. Mutations were found in patients with Pendred syndrome and nonsyndromic EVA with or without Mondini dysplasia. Mutations were not detected in patients with isolated Mondini dysplasia. One proband with clinical diagnosis Pendred syndrome was homozygous for the c.35delG mutation in the GJB2 gene. The absence of frequent mutations, including well-known ones or “hot” exons in the SLC26A4 gene, was reported. Therefore, the optimal method to search for mutations in the SLC26A4 gene in Russian patients is Sanger sequencing of all exons and exon-intron boundaries in the SLC26A4 gene.     

Optimization of Nutrients and Culture Conditions for Alkaline Protease Production Using Two Endophytic Micrococci: <Emphasis Type="Italic">Micrococcus aloeverae</Emphasis> and <Emphasis Type="Italic">Micrococcus yunnanensis</Emphasis>

An endophytic species of Micrococcus was isolated from Aloe vera leaf (syn. Aloe barbadensis) and screened for protease production with five other species of Micrococcus. Data indicated that endophytic Micrococcus aloeverae AE-6 MCC 2184^T and Micrococcus yunnanensis DSM 21948^T showed efficient protease production potential and secreted active protease at high salt (10%), temperature (40 °C) and in wide range of pH 8–10. Unlike M. yunnanensis DSM 21948^T, protease production by M. aloeverae AE-6 MCC 2184^T was stringently controlled by pH. Protease induction study using different group of peptides, peptide carbohydrates and peptide macronutrient combinations showed variable response with both the organisms. Result indicated that the amount of protease was not directly related to cell biomass but it depends on nature of inducible peptides. In this study we also developed a modified agar-well assay for semi-quantitative data from large number of replicates.     

Occurrence and distribution of multiple antibiotic-resistant <Emphasis Type="Italic">Enterococcus</Emphasis> and <Emphasis Type="Italic">Lactobacillus</Emphasis> spp. from Indian poultry: in vivo transferability of their erythromycin,tetracycline and vancomycin resistance

The objective of this study was to determine the occurrence and distribution of antibiotic resistant (AR) lactic acid bacteria (LAB) in Indian poultry. LAB from poultry farm feces (n = 21) and samples from slaughter houses comprising chicken intestine (n = 46), raw meat (n = 23), and sanitary water (n = 4) were evaluated and compared with those from organic chicken (OC) collected from nearby villages. Screening studies showed 5–7 log units higher erythromycin (ER), tetracycline (TC) and vancomycin (VAN) resistant LAB from conventional poultry chicken (CC) compared to OC. Molecular characterization of isolated cultures (n = 32) with repetitive-PCR profiling and 16S rRNA gene sequencing revealed their taxonomical status as Enterococcus faecium (n = 16), Enterococcus durans (n = 2), Lactobacillus plantarum (n = 10), Lactobacillus pentosus (n = 1) and Lactobacillus salivarius (n = 3). The isolates were found to harbor erm(B), msr(C), msr(A/B), tet(M), tet(L) and tet(K) genes associated with Tn916 and Tn917 family transposons. Expression studies through real-time PCR revealed antibiotic-induced expression of the identified AR genes. In vitro and in vivo conjugational studies revealed transfer of ER and TC resistant (ER^R and TC^R) genes with transfer frequencies of 10^?7 and 10^?4 transconjugants recipient^?1, respectively. Although no known VAN resistance (VAN^R) genes were detected, high phenotypic resistance was observed and was transferable to the recipient. From a public health point of view, this study reports Indian poultry as a major source of high levels of AR bacteria contaminating the food chain and the environment. Thus, urgent and determined strategies are needed to control the spread of multiple AR bacteria.     

Shengmai Formula Ameliorates Pathological Characteristics in AD <Emphasis Type="Italic">C.</Emphasis> <Emphasis Type="Italic">elegans</Emphasis>

Shengmai (SM) formula, a classical traditional Chinese medicine formula, is composed of Panax ginseng (Pg), Ophiopogon japonicus (Oj), and Schisandra Chinesis (Sc). SM has been clinically used to treat heart failure and ischemic heart disease. Although SM formula has been reported to be potential for fighting against Alzheimer’s disease (AD) by previous works, there are many gaps in our knowledge on its usage in AD treatment on an organism level and will then need to be further clarified. In this study, transgenic Caenorhabditis elegans expressing human Aβ_1–42 are used to evaluate SM formula efficacy to treat AD phenotype and to investigate its underlying mechanism. The results showed that SM formula ameliorated AD pathological characteristics of paralysis behavior and chemotaxis defect in transgenic C. elegans. With SM treatment, the number of Aβ deposits decreased, the levels of gene expressions of hsp16-2, hsp16-41, ace-1, ace-2, and TNFA1P1 homolog genes were down-regulated. Our results also showed that Oj exhibited more stronger effect on delaying paralysis in worms than Pg and Sc did, and synergistic action was observed between Pg and Oj, and Sc further enhanced the activity of Pg/Oj combination on delaying paralysis behavior. Further, SM with herbs of Pg, Oj, and Sc at a dose proportion of 9:9:6 exhibited superior therapeutic efficacy in comparison with herbs at other dose proportions. After SM formula extracted by ethanol, it delayed AD symptoms on a wider dose from 0.2 to 10.0 mg/mL with no toxic effect. These results provided more evidence for SM formula being potential to be used to treat AD.     

The protection of novel 2-arylethenylquinoline derivatives against impairment of associative learning memory induced by neural Aβ in <Emphasis Type="Italic">C. elegans</Emphasis> Alzheimer’s disease model

Cerebral deposition of amyloid β-peptide (Aβ), a fundamental feature of Alzheimer’s disease (AD), damages the neurocytes and impairs the cognition functions and associative learning memory of AD patients. A series of novel 2-arylethenylquinoline derivatives were synthesized and evaluated in our previous study, which inhibited Aβ aggregation in vitro effectively at the concentration of 20 μmol/L and exhibited high antioxidant activity. In order to verify the capacity of anti-AD in vivo, the transgenic Caenorhabditis elegans (C. elegans) strain CL2355 expressing neural Aβ was employed as the AD model to investigate the neuroprotective activity of seven high-potential compounds (4a1, 4a2, 4b1, 4b2, 4c1, 4c2, 4c3) selected from those derivatives. Learning memory associated chemotaxis assay was performed to evaluate the neural repairment capacity. The underlying mechanism was investigated by mRNA analysis of Aβ gene and heat shock protein genes (hsp-16.1 and hsp-16.2) and Western blot of Aβ. Our data indicated that among seven tested compound, 4b1 and 4c2 reduced Aβ-induced stress, suppressed the expression of neural Aβ monomers and toxic oligomers, and recovered the damaged associative learning memory in C. elegans AD model. These findings further confirmed their potentials to become valuable agents for AD therapy.     

DNA copy number analysis of the DFNB1 hereditary hearing loss locus

Recessive mutations in the GJB2 gene and large deletions of the cis-regulatory element of this gene are the main causes of congenital nonsyndromic sensorineural hearing loss in many countries, including Russia. Large deletions represent 0.3–10% of all alleles in the DFNB1 locus in different populations and are usually observed in compound heterozygous state with intragenic mutations or are rarely observed in the homozygous or compound-heterozygous state with another large deletion. According to published studies, six large deletions exist, including three frequent deletions del(GJB6-D13S1830), del(GJB6-D13S1854), and del(GJB2-D13S175) and three rare deletions observed in single cases. The present study describes the results of the copy number analysis of the GJB2 regulatory region for the detection of unknown deletions in patients with a single heterozygous recessive intragenic mutation. Additionally, a quantitative analysis of GJB2 and GJB6 gene sequences in individuals bearing homozygous mutation in the GJB2 gene, which might also have mutation in the hemizygous state, is performed. The system for quantitative analysis of the region including the regulatory element of the GJB2 gene based on the MLPA® approach is developed. Moreover, a commercial kit of reagents is used for the detection of copy number of the GJB2 and GJB6 genes by the same method. As a result of the conducted analysis, no changes in copy number are detected in the explored regions. Obviously, if Russian patients have mutations in unidentified regulatory or other regions of the DFNB1 locus, frequency of such unidentified mutations is extremely rare.     

SORL1 Is Associated with the Risk of Late-Onset Alzheimer’s Disease: a Replication Study and Meta-Analyses

The sorting-related receptor gene (SORL1) has been defined as an interesting candidate gene for Alzheimer’s disease (AD). Recently, one novel variant, rs11218343, within SORL1 was reported to be related to late-onset Alzheimer’s disease (LOAD) in Caucasians, Korean, and Japanese. The aim of this case–control study is to investigate whether SORL1 rs11218343 contributes to susceptibility for LOAD in Chinese. Furthermore, our data, along with previously studies, were pooled for determining the risk of the rs11218343 polymorphism on LOAD. The rs11218343 polymorphism was genotyped in the 2350 independent subjects from Northern Han Chinese population (including 992 cases and 1358 age- and gender-matched controls). Result of the case–control study showed the association between rs11218343 polymorphism and the risk of LOAD in a Northern Han Chinese population (recessive model: odds ratio (OR)?=?0.641, 95 % confidence interval (CI)?=?0.464–0.884, P?=?0.007; additive model: OR?=?0.873, 95 % CI?=?0.765–0.996, P?=?0.043). The results of meta-analysis in subgroups (Caucasian and Asian) and the whole showed that the minor allele (C allele) within rs11218343 played a protective effect on AD risk (OR (95 % CI), 0.77 (0.72–0.83), 0.85 (0.79–0.91), 0.81 (0.76–0.85), respectively). In conclusion, the C allele in SORL1 rs11218343 may be a protective factor for LOAD in both Caucasian and Han Chinese.     

Functional alterations of myeloid cells during the course of Alzheimer’s disease

Background

Neuroinflammation is a hallmark of neurodegenerative disease and a significant component of the pathology of Alzheimer’s disease (AD). Patients present with extensive microgliosis along with elevated pro-inflammatory signaling in the central nervous system and periphery. However, the role of peripheral myeloid cells in mediating and influencing AD pathogenesis remains unresolved.

Methods

Peripheral myeloid cells were isolated from peripheral blood of patients with prodromal AD (n =?44), mild AD dementia (n =?25), moderate/severe AD dementia (n =?28), and age-matched controls (n =?54). Patients were evaluated in the clinic for AD severity and categorized using Clinical Dementia Rating (CDR) scale resulting in separation of patients into prodromal AD (CDR0.5) and advancing forms of AD dementia (mild-CDR1 and moderate/severe-CDR2/3). Separation of peripheral myeloid cells into mature monocytes or immature MDSCs permitted the delineation of population changes from flow cytometric analysis, RNA phenotype analysis, and functional studies using T cell suppression assays and monocyte suppression assays.

Results

During stages of AD dementia (CDR1 and 2/3) peripheral myeloid cells increase their pro-inflammatory gene expression while at early stages of disease (prodromal AD—CDR0.5) pro-inflammatory gene expression is decreased. MDSCs are increased in prodromal AD compared with controls (16.81% vs 9.53%) and have markedly increased suppressive functions: 42.4% suppression of activated monocyte-produced IL-6 and 78.16% suppression of T cell proliferation. In AD dementia, MDSC populations are reduced with decreased suppression of monocyte IL-6 (5.22%) and T cell proliferation (37.61%); the reduced suppression coincides with increased pro-inflammatory signaling in AD dementia monocytes.

Conclusions

Peripheral monocyte gene expression is pro-inflammatory throughout the course of AD, except at the earliest, prodromal stages when pro-inflammatory gene expression is suppressed. This monocyte biphasic response is associated with increased numbers and suppressive functions of MDSCs during the early stages and decreased numbers and suppressive functions in later stages of disease. Prolonging the early protective suppression and reversing the later loss of suppressive activity may offer a novel therapeutic strategy.

     

<Emphasis Type="Italic">ABI3</Emphasis> and <Emphasis Type="Italic">PLCG2</Emphasis> missense variants as risk factors for neurodegenerative diseases in Caucasians and African Americans

Background

Rare coding variants ABI3_rs616338-T and PLCG2_rs72824905-G were identified as risk or protective factors, respectively, for Alzheimer’s disease (AD).

Methods

We tested the association of these variants with five neurodegenerative diseases in Caucasian case-control cohorts: 2742 AD, 231 progressive supranuclear palsy (PSP), 838 Parkinson’s disease (PD), 306 dementia with Lewy bodies (DLB) and 150 multiple system atrophy (MSA) vs. 3351 controls; and in an African-American AD case-control cohort (181 AD, 331 controls). 1479 AD and 1491 controls were non-overlapping with a prior report.

Results

Using Fisher’s exact test, there was significant association of both ABI3_rs616338-T (OR?=?1.41, p?=?0.044) and PLCG2_rs72824905-G (OR?=?0.56, p?=?0.008) with AD. These OR estimates were maintained in the non-overlapping replication AD-control analysis, albeit at reduced significance (ABI3_rs616338-T OR?=?1.44, p?=?0.12; PLCG2_rs72824905-G OR?=?0.66, p?=?0.19). None of the other cohorts showed significant associations that were concordant with those for AD, although the DLB cohort had suggestive findings (Fisher’s test: ABI3_rs616338-T OR?=?1.79, p?=?0.097; PLCG2_rs72824905-G OR?=?0.32, p?=?0.124). PLCG2_rs72824905-G showed suggestive association with pathologically-confirmed MSA (OR?=?2.39, p?=?0.050) and PSP (OR?=?1.97, p?=?0.061), although in the opposite direction of that for AD. We assessed RNA sequencing data from 238 temporal cortex (TCX) and 224 cerebellum (CER) samples from AD, PSP and control patients and identified co-expression networks, enriched in microglial genes and immune response GO terms, and which harbor PLCG2 and/or ABI3. These networks had higher expression in AD, but not in PSP TCX, compared to controls. This expression association did not survive adjustment for brain cell type population changes.

Conclusions

We validated the associations previously reported with ABI3_rs616338-T and PLCG2_rs72824905-G in a Caucasian AD case-control cohort, and observed a similar direction of effect in DLB. Conversely, PLCG2_rs72824905-G showed suggestive associations with PSP and MSA in the opposite direction. We identified microglial gene-enriched co-expression networks with significantly higher levels in AD TCX, but not in PSP, a primary tauopathy. This co-expression network association appears to be driven by microglial cell population changes in a brain region affected by AD pathology. Although these findings require replication in larger cohorts, they suggest distinct effects of the microglial genes, ABI3 and PLCG2 in neurodegenerative diseases that harbor significant vs. low/no amyloid ß pathology.