Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

A repeat-primed PCR assay for pentanucleotide repeat alleles in spinocerebellar ataxia type 37


Spinocerebellar ataxia 37 (SCA37) is caused by an (ATTTC)n insertion in a polymorphic ATTTT repeat in the non-coding region of DAB1. The non-pathogenic alleles have a configuration [(ATTTT)7–400], whereas pathogenic alleles have a complex structure of [(ATTTT)60–79(ATTTC)31–75(ATTTT)58–90]. Molecular diagnosis of SCA37 is laborious because about 7% of the pentanucleotide repeat alleles in DAB1 are larger than 30 units and, thus, fail to amplify with standard PCR conditions, resulting in apparently homoallelism or in complete lack of PCR amplification in several cases. The molecular test currently available requires long-range PCR and sequencing analysis for the detection and characterization of these large alleles. We developed a simple assay capable of rapidly detecting the presence or absence of large pentanucleotide repeat sizes. This assay is based on repeat-primed PCR followed by high-throughput capillary electrophoresis. Combining the standard PCR with RP-PCR allows completion of the diagnosis in more than 80% of individuals, minimizing the number of samples that require long-range PCR followed by Sanger sequencing analysis. This assay meets many of the requirements for pre-screening of large cohorts of affected individuals.

This is a preview of subscription content

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1
Fig. 2
Fig. 3


  1. 1.

    Loureiro JR, Oliveira CL, Silveira I. Unstable repeat expansions in neurodegenerative diseases: nucleocytoplasmic transport emerges on the scene. Neurobiol Aging. 2016;39:174–83.

    Article  PubMed  CAS  Google Scholar 

  2. 2.

    Sequeiros J, Martins S, Silveira I. In Handbook of Clinical Neurology Vol. 103, pp. 227–51, (Netherlands 2012).

  3. 3.

    Huang M, Verbeek DS. Why do so many genetic insults lead to Purkinje Cell degeneration and spinocerebellar ataxia? Neurosci Lett. (2018)

  4. 4.

    Paulson HL, Shakkottai VG, Clark HB, Orr HT. Polyglutamine spinocerebellar ataxias—from genes to potential treatments. Nat Rev Neurosci. 2017;18:613–26.

    Article  PubMed  CAS  Google Scholar 

  5. 5.

    Coutinho P, Ruano L, Loureiro J, Cruz V, Barros J, Tuna A, et al. Hereditary ataxia and spastic paraplegia in Portugal: a population-based prevalence study. JAMA Neurol. 2013;70:746–55.

    Article  PubMed  Google Scholar 

  6. 6.

    Nelson DL, Orr HT, Warren ST. The unstable repeats–three evolving faces of neurological disease. Neuron. 2013;77:825–43.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  7. 7.

    Garcia-Murias M, Quintans B, Arias M, Seixas AI, Cacheiro P, Tarrio R, et al. ‘Costa da Morte’ ataxia is spinocerebellar ataxia 36: Clinical and genetic characterization. Brain. 2012;135:1423–35.

    Article  PubMed  PubMed Central  Google Scholar 

  8. 8.

    Alonso I, Jardim L, Artigalas O, Saraiva-Pereira M, Matsuura T, Ashizawa T, et al. Reduced penetrance of intermediate size alleles in spinocerebellar ataxia type 10. Neurology. 2006;66:1602–4.

    Article  PubMed  CAS  Google Scholar 

  9. 9.

    Silveira I, Alonso I, Guimarães L, Mendonça P, Santos C, Maciel P, et al. High germinal instability of the (CTG)n at the SCA8 locus of both expanded and normal alleles. Am J Hum Genet. 2000;66:830–40.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  10. 10.

    Silveira I, Miranda C, Guimaraes L, Moreira M, Alonso I, Mendonca P, et al. Trinucleotide repeats in 202 families with ataxia - A small expanded (CAG)(n) allele at the SCA17 locus. Arch Neurol. 2002;59:623–9.

    Article  PubMed  CAS  Google Scholar 

  11. 11.

    Seixas AI, Vale J, Jorge P, Marques I, Santos R, Alonso I, et al. FXTAS is rare among Portuguese patients with movement disorders: FMR1 premutations may be associated with a wider spectrum of phenotypes. Behav Brain Funct. 2011;7:19.

    Article  PubMed  PubMed Central  Google Scholar 

  12. 12.

    Sato N, Amino T, Kobayashi K, Asakawa S, Ishiguro T, Tsunemi T, et al. Spinocerebellar ataxia type 31 is associated with “inserted” penta-nucleotide repeats containing (TGGAA)n. Am J Hum Genet. 2009;85:544–57.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  13. 13.

    Seixas AI, Loureiro JR, Costa C, Ordonez-Ugalde A, Marcelino H, Oliveira CL, et al. A pentanucleotide ATTTC repeat insertion in the non-coding region of DAB1, mapping to SCA37, causes Spinocerebellar Ataxia. Am J Hum Genet. 2017;101:87–103.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  14. 14.

    Ishikawa K, Dürr A, Klopstock T, Müller S, De Toffol B, Vidailhet M, et al. Pentanucleotide repeats at the spinocerebellar ataxia type 31 (SCA31) locus in Caucasians. Neurology. 2011;77:1853–5.

    Article  PubMed  CAS  Google Scholar 

  15. 15.

    Cagnoli C, Michielotto C, Matsuura T, Ashizawa T, Margolis RL, Holmes SE, et al. Detection of large pathogenic expansions in FRDA1, SCA10, and SCA12 genes using a simple fluorescent repeat-primed PCR assay. J Mol Diagn. 2004;6:96–100.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

  16. 16.

    Chen L, Hadd A, Sah S, Filipovic-Sadic S, Krosting J, Sekinger E, et al. An information-rich CGG repeat primed PCR that detects the full range of fragile X expanded alleles and minimizes the need for southern blot analysis. J Mol Diagn. 2010;12:589–600.

    Article  PubMed  PubMed Central  CAS  Google Scholar 

Download references


This work was funded by Fundo Europeu de Desenvolvimento Regional-FEDER funds through the COMPETE 2020—Operational Programme for Competitiveness and Internationalisation (POCI), Portugal 2020, and by funding from FCT—Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia e Inovação, Portugal, in the framework of the project “Institute for Research and Innovation in Health Sciences” (POCI-01-0145-FEDER-007274); by Grant PTDC/SAU-GMG/098305/2008, from FCT, to I.S. J.R.L. was supported by scholarships from Grant PTDC/GMG-SAU/098305/2008, FCT, PEst-C/SAU/LA0002/2013 and EMBO (ASTF494-2015). C.L.O. was supported by a scholarship from PEst-C/SAU/LA0002/2013. This work was also funded by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (FEDER), Portugal, that supports the Norte-01-0145-FEDER-000008—Porto Neurosciences and Neurologic Disease Research Initiative at I3S.

Author information



Corresponding author

Correspondence to Isabel Silveira.

Ethics declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Loureiro, J.R., Oliveira, C.L., Sequeiros, J. et al. A repeat-primed PCR assay for pentanucleotide repeat alleles in spinocerebellar ataxia type 37. J Hum Genet 63, 981–987 (2018).

Download citation


Quick links