Parkinsonism and Related Disorders 19 (2013) 487–489
Contents lists available at SciVerse ScienceDirect
Parkinsonism and Related Disorders journal homepage: www.elsevier.com/locate/parkreldis
Letter to the Editor
Genetic study on frontotemporal lobar degeneration in India Keywords: APOE FTLD Gene dosage MAPT PGRN SNP
Frontotemporal lobar degeneration (FTLD) [MIM#600274] is a clinically and pathologically heterogeneous syndrome, characterized by progressive deterioration in behavior and/or language associated with either symmetric or asymmetric degeneration of frontal and/or anterior temporal lobes of the brain. Its prevalence varies between 2.7 and 15 per 100,000. Used as an umbrella term FTLD includes diseases like behavioral variant of frontotemporal dementia (bvFTD), primary progressive aphasia (PPA), semantic dementia (SD), frontotemporal dementia with motor neuron disease (FTD-MND), corticobasal degeneration (CBD) and progressive supranuclear palsy (PSP) [1]. Apart from the hexanucleotide repeat expansion in C9ORF72, Microtubule associated protein tau (MAPT) [MIM#157140] and Progranulin (PGRN) [MIM#138945] account for the majority of mutations in FTLD. Among other genetic susceptibility factors that can modulate FTLD, the roles of MAPT haplotypes and apolipoprotein epsilon (APOE) genotypes are relevant. However, in spite of worldwide studies on the molecular basis of FTLD over the past years there is no report on the genetic study of FTLD from India. This led us to study the molecular bases of FTLD pathogenesis using MAPT and PGRN as candidate genes, while MAPT haplotypes and APOE genotypes were studied for their potential association with the conditions. Eighty one FTLD patients (19 bvFTD, 3 SD, 4 PPA, 3 FTD-MND, 48 PSP and 4 CBD) diagnosed at the Cognitive and Movement Disorders Clinics of Bangur Institute of Neurosciences, Kolkata and Apollo Gleneagles Hospitals, Kolkata; and 269 healthy controls were recruited to take part in this study. Diagnosis of the cases was based on standard clinical features history, examination and imaging. However, in the absence of autopsy data, final diagnosis could not be fully confirmed. Exons 0–12 of PGRN and exons 1, 9– 13 of MAPT were PCR amplified and then bi-directionally sequenced along with intron-exon boundaries. In addition, MAPT H1-H2 haplotype status of each subject was determined by PCR, whereas APOE genotyping was done by PCR-RFLP. Gene dosage analysis of MAPT and PGRN was done according to manufacturer’s protocol for multiplex ligation-dependent probe amplification (MLPA) assay using commercially available probes (SALSA MLPA P275-B1 MAPTGRN probemix, MRC Holland, Amsterdam, the Netherlands). In 1353-8020/$ – see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.parkreldis.2012.11.015
selected individuals Progranulin expression levels were determined in triplicate from plasma samples using human Progranulin ELISA kit (Adipogen Inc., Seoul, Korea). The study was approved by the institutional review board and every participant were included in the study only after taking written and informed consent from them or their nearest family member. We identified 11 nucleotide variants in MAPT including 3 novel polymorphisms whereas for PGRN 3 out of 8 identified variants were novel (Table 1). None of the novel variants were predicted to alter amino acid sequence, splicing pattern or miRNA binding site. Since rs5848, a potential risk factor for FTLD, lies in the binding site of miR-659, we next estimated plasma Progranulin in 30 controls (Fig. 1). Individuals with T/T genotype at rs5848 had a marginally decreased expression of PGRN than C/C individuals (p ¼ 0.042) corroborating a recent study where T/T individuals had decreased Progranulin expression in control and other dementias sub-group [2]. However, due to lack of available plasma samples we could not estimate Progranulin level among our subjects. Gene dosage study was done in FTLD cases (except PSP) by MLPA and the relative amount of the products of MAPT and PGRN probes in the patients were within the threshold levels of 0.75–1.25 when compared to the reference probes suggesting a normal copy number of the above mentioned genes in the studied samples (data not shown). Except one PSP patient all were homozygous for MAPT H1 haplotype (data not shown) and there was no significant difference in the distribution of MAPT haplotypes in either patients or controls. In addition, APOE genotyping in 81 FTLD cases and 269 controls revealed no biased distribution in either of the two groups (Supplementary Table 1) suggesting that APOE is not a susceptible locus for FTLD pathogenesis among Indians. In the present study we screened 81 Indian FTLD patients for mutation in MAPT whereas for PGRN all the patients (n ¼ 33) except PSP were included as to date no causative mutation has been identified in PGRN among PSP patients. We, failed to find any pathogenic mutation in any of these genes, nor were we able to find any copy number variation in them. In fact, gene dosage alteration in MAPT and PGRN is a rare cause of FTLD. MAPT mutations are common among familial cases and have been observed to have founder
488
Letter to the Editor / Parkinsonism and Related Disorders 19 (2013) 487–489
Table 1 MAPT and PGRN variants identified among Indian FTLD patients. Gene
Variant
Amino acid
Location
No. of chromosomes Cases
MAPT
PGRN
c.1 13A > G c.1686A > G c.1770T > C c.1803G > A c.1815G > A c.1827 þ 103G > A c.1843 176G > A c.1843 47C > T c.2002 þ 34G > A c.2331 þ 26T > C c.2331 þ 64G > A c.1 3916C > A c.1 3784G INS c.1 3273C > T c.264 þ 21G > A c.267C > T c.462 þ 24G > A c.384T > C c.1782 þ 78C > T
– p.Ala227Ala p.Asn255Asn p.Lys266Lys p.Pro270Pro – – – – – – – – – – p.Ala89Ala – p.Asp128Asp –
50 UTR Exon 9 Exon 9 Exon 9 Exon 9 Intron 9 Intron 9 Intron 10 Intron 11 30 UTR 30 UTR Exon 0 Intron 0 Intron 0 Intron 2 Exon 3 Intron 4 Exon 5 30 UTR
1/162 2/162 1/162 2/162 2/162 6/162 33/162 1/162 2/162 1/162 9/162 1/66 30/66 43/66 15/66 1/66 11/66 10/66 16/66
Status Controls
(0.006) (0.012) (0.006) (0.012) (0.012) (0.037) (0.204) (0.006) (0.012) (0.006) (0.055) (0.015) (0.454) (0.651) (0.227) (0.015) (0.167) (0.152) (0.242)
ND ND ND ND 4/144 (0.028) ND ND ND ND ND ND ND ND ND ND ND ND ND 28/60 (0.467)
rs17650901 rs1052553 rs17652121 Reported rs11568305 rs117562189 rs41543317 Novel Novel rs9468 Novel Novel Novel rs3859268 rs9897526 Novel rs850713 rs25646 rs5848
rs# taken from dbSNP; ND, not determined. cDNA numbering of MAPT is relative to BN000503.1 and starting at nt 1, i.e., the translation initiation site; Protein numbering of MAPT according to the GenPept Accession Number CAG26750.1. cDNA numbering of PGRN is relative to NM_002087.2 starting at ATG; Protein numbering according to the largest progranulin isoforms (GenPept Accession Number NP_002078.1).
effect in the Netherlands and France. Its frequency is low in Sweden and Poland, and absent in Finland. From Japan 6 MAPT mutations have been reported [3,4] whereas among Koreans it is absent. Mutation in PGRN is a common cause of FTLD among Belgian, French and US populations, accounting for 5–11% of sporadic and 20–25% of familial cases; however, it is low among Portuguese, Italians and Germans, and completely absent in Finns. To date only an insertion–deletion mutation in PGRN has been identified in a Japanese cohort [4] suggesting that mutation in this gene is rare among the Asians. Therefore, it appears that geographical and ethnic variations might be responsible for the diverse frequency in MAPT and PGRN mutations worldwide. It is also possible that the size of our patient cohort is not large enough to find mutations in these genes if the occurrence of mutations is relatively rare. A previous study has demonstrated an association with APOE and frontotemporal dementia but a later study was unable to replicate this association among FTLD samples [5]. APOE is a major protein which plays several important roles in response to brain injury and our result shows no association of this gene the pathogenesis in FTLD.
Our results suggest that MAPT, PGRN and APOE play limited roles in FTLD pathogenesis among Indians. Future studies should be conducted on larger sample size to evaluate more comprehensively the contribution of these genes in Indian FTLD patients. To our knowledge this is the first genetic study on FTLD among Indians. Acknowledgments The authors thank all the participants in the study. This study was partially supported by University Grants Commission (UGC), India [Grant No. F.14-38/2007 (Inno/ASIST)], Council of Scientific and Industrial Research (CSIR), India, Ministry of Earth Sciences (MoES), India and pre-doctoral fellowships to GD (CSIR), TS (Government of West Bengal, India) and DS (UGC). Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.parkreldis.2012.11.015.
References
Fig. 1. Plasma Progranulin level among individuals carrying different genotypes of rs5848. Individuals with C/C genotype had the highest level of plasma Progranulin followed by those with C/T and T/T genotypes. Mann–Whitney test revealed that Progranulin level is marginally decreased among T/T individuals compared to those with C/C genotype (p ¼ 0.042). Error bars indicate standard deviation; * represents statistical significance (p 0.05).
[1] Josephs KA. Frontotemporal dementia and related disorders: deciphering the enigma. Ann Neurol 2008;64:4–14. [2] Hsiung GY, Fok A, Feldman HH, Rademakers R, Mackenzie IR. rs5848 polymorphism and serum progranulin level. J Neurol Sci 2010;300:28–32. [3] Kowalska A, Asada T, Arima K, Kumakiri C, Kozubski W, Takahashi K, et al. Genetic analysis in patients with familial and sporadic frontotemporal dementia: two tau mutations in only familial cases and no association with apolipoprotein epsilon4. Dement Geriatr Cogn Disord 2001;12:387–92. [4] Ogaki K, Li Y, Takanashi M, Ishikawa KI, Kobayashi T, Nonaka T, et al. Analyses of the MAPT, PGRN, and C9orf72 mutations in Japanese patients with FTLD, PSP, and CBS. Parkinsonism Relat Disord 2013 Jan;19(1):15–20. [5] Lovati C, Galimberti D, Albani D, Bertora P, Venturelli E, Cislaghi G, et al. APOE epsilon2 and epsilon4 influence the susceptibility for Alzheimer’s disease but not other dementias. Int J Mol Epidemiol Genet 2010;1:193–200.
Gautami Das, Tamal Sadhukhan, Dipanwita Sadhukhan S. N. Pradhan Centre for Neurosciences, University of Calcutta, 35, Ballygunge Circular Road, Kolkata – 700 019, India
Letter to the Editor / Parkinsonism and Related Disorders 19 (2013) 487–489
Atanu Biswas Movement Disorders Clinic, Bangur Institute of Neurosciences, Kolkata, India Sandip Pal Movement Disorders Clinic, Bangur Institute of Neurosciences, Kolkata, India Department of Neurology, Burdwan Medical College and Hospital, West Bengal Health University, India Amitabha Ghosh Department of Neurology, Apollo Gleneagles Hospitals, Kolkata, India Shyamal K. Das Movement Disorders Clinic, Bangur Institute of Neurosciences, Kolkata, India
489
Department of Neurology, Burdwan Medical College and Hospital, West Bengal Health University, India Kunal Ray Molecular & Human Genetics Division, CSIR-Indian Institute of Chemical Biology, Kolkata, India Jharna Ray* S. N. Pradhan Centre for Neurosciences, University of Calcutta, 35, Ballygunge Circular Road, Kolkata – 700 019, India * Corresponding author. Tel.: þ91 94330 31773. E-mail addresses:
[email protected],
[email protected] (J. Ray) 13 July 2012
