A novel seven-octapeptide repeat insertion in the prion protein gene (PRNP) in a Dutch pedigree with Gerstmann-Sträussler-Scheinker disease phenotype: comparison with similar cases from the literature

Abstract

Human prion diseases can be sporadic, inherited or acquired by infection and show considerable phenotypic heterogeneity. We describe the clinical, histopathological and pathological prion protein (PrP(Sc)) characteristics of a Dutch family with a novel 7-octapeptide repeat insertion (7-OPRI) in PRNP, the gene encoding the prion protein (PrP). Clinical features were available in four, neuropathological features in three and biochemical characteristics in two members of this family. The clinical phenotype was characterized by slowly progressive cognitive decline, personality change, lethargy, depression with anxiety and panic attacks, apraxia and a hypokinetic-rigid syndrome. Neuropathological findings consisted of numerous multi- and unicentric amyloid plaques throughout the cerebrum and cerebellum with varying degrees of spongiform degeneration. Genetic and molecular studies were performed in two male family members. One of them was homozygous for valine and the other heterozygous for methionine and valine at codon 129 of PRNP. Sequence analysis identified a novel 168 bp insertion [R2-R2-R2-R2-R3g-R2-R2] in the octapeptide repeat region of PRNP. Both patients carried the mutation on the allele with valine at codon 129. Western blot analysis showed type 1 PrP(Sc) in both patients and detected a smaller ~8 kDa PrP(Sc) fragment in the cerebellum in one patient. The features of this Dutch kindred define an unusual neuropathological phenotype and a novel PRNP haplotype among the previously documented 7-OPRI mutations, further expanding the spectrum of genotype-phenotype correlations in inherited prion diseases.

Fig. 1

Pedigree of the family described in this manuscript. Circles indicate females; squares correspond to males. Affected family members are shown in shaded symbols, unaffected individuals in open symbols. A diagonal bar in a symbol indicates a deceased family member. The question mark indicates a clinical history suggestive of prion disease, albeit not neuropathologically proven. The numbers refer to the case numbers in the text

Fig. 2

Histopathological findings in two family members (III-4 and III-6) with 7-OPRI. Sections are stained with haematoxylin–eosin (a, b, e, f, g and h) and the 3F4 anti-PrP antibody (c, d, j and k), original magnification ×200. Mild (a) and severe (b) spongiform change in the frontal cortex; c, d multicentric and unicentric plaques in the frontal cortex; e mild spongiform change with multicentric plaques (arrows) in the caudate nucleus; f severe spongiform change in the caudate nucleus; g, j many multicentric plaques in the molecular layer of the cerebellum; h, k moderate spongiform change with multicentric plaques (arrow) in the molecular layer of the cerebellum

Fig. 3

Western blot analysis of two family members (III-4 and III-6) with 7-OPRI. In a protease-resistant prion protein (PrP^res) from specimens of temporal cortex (TC) and cerebellum (Cb) from one patient (III-4) and from specimens of temporal cortex (TC) and occipital cortex (OC) from the other patient (III-6) are shown flanked by reference standards of frontal cortex from sporadic CJD of the MM1 subtype (1) and frontal cortex from variant CJD (2B). In b the relative abundance of the three different glycoforms of PrP^res is shown, calculated on the basis of densitometric analysis of three independent samples from the available frozen tissues shown in a. The relative abundance of the upper (diglycosylated) band is shown in black, the middle (monoglycosylated) band is shown in grey and the lower (non-glycosylated) band is shown in white. In c the PrP^res profile from the cerebellum in patient III-4 (III-4 Cb) is compared with those found in a patient with Gerstmann–Sträussler–Scheinker disease carrying a proline to leucine substitution at position 102 (GSS P102L), and samples from the temporal cortex and occipital cortex of a Dutch case of protease sensitive prionopathy (PSPr TC and PSPr OC). M denotes molecular weight markers with their M _r indicated in kDa. The loading of individual samples on Western blots (volume of 10% weight/volume brain homogenate) was adjusted to allow easy comparison of the PrP^res profiles obtained. All densitometric readings for glycoform analysis were within the linear range for each band in every sample