A novel ECM1\it ECM1 splice site mutation in lipoid proteinosis

Lipoid proteinosis (LP) is an autosomal recessive genodermatosis known to be caused by mutations in $\it ECM1$. Nonsense and missense mutations are the most common variations in LP. Up to date, only 6 splice site mutations have been observed. We report on a 26-year-old female LP patient from a Turkish consanguineous family carrying a novel homozygous splice site mutation in intron 8 of the $\it ECM1$ gene and summarize the current knowledge on $\it ECM1$ mutations and possible genotype-phenotype correlations

Investigation of sex-specific effects of apolipoprotein E on severity of EAE and MS

$\textbf {Background:}$ Despite pleiotropic immunomodulatory effects of apolipoprotein E (apoE) $\textit {in vitro}$, its effects on the clinical course of experimental autoimmune encephalomyelitis (EAE) and multiple sclerosis (MS) are still controversial. As sex hormones modify immunomodulatory apoE functions, they may explain contentious findings. This study aimed to investigate sex-specific effects of $\it apoE$ on disease course of EAE and MS. $\textbf {Methods:}$ $MOG_{35-55}$ induced EAE in female and male $\it apoE$-deficient mice was assessed clinically and histopathologically. $\it apoE$ expression was investigated by qPCR. The association of the MS severity score (MSSS) and $\it APOE$ rs429358 and rs7412 was assessed across 3237 MS patients using linear regression analyses. $\textbf {Results:}$ EAE disease course was slightly attenuated in male $\it apoE$-deficient $\it (apoE^{-/-})$ mice compared to wildtype mice (cumulative median score: $\it apoE^{-/-}$ = 2 [IQR 0.0–4.5]; wildtype = 4 [IQR 1.0–5.0]; $\it n$ = 10 each group, $\it p$ = 0.0002). In contrast, EAE was more severe in female $\it apoE^{-/-}$ mice compared to wildtype mice (cumulative median score: $\it apoE^{-/-}$ = 3 [IQR 2.0–4.5]; wildtype = 3 [IQR 0.0–4.0]; $\it n$ = 10, $\it p$= 0.003). In wildtype animals, $\it apoE$ expression during the chronic EAE phase was increased in both females and males (in comparison to naïve animals; $\it p$< 0.001). However, in MS, we did not observe a significant association between MSSS and rs429358 or rs7412, neither in the overall analyses nor upon stratification for sex. $\textbf {Conclusions:}$ $\it apoE$ exerts moderate sex-specific effects on EAE severity. However, the results in the $\it apoE$ knock-out model are not comparable to effects of polymorphic variants in the human $\it APOE$ gene, thus pinpointing the challenge of translating findings from the EAE model to the human disease

Frequency of SCA8, SCA10, SCA12, SCA36, FXTAS\textit {SCA8, SCA10, SCA12, SCA36, FXTAS} and C9orf72\it C9orf72 repeat expansions in SCA patients negative for the most common SCA subtypes

$\textbf {Background:}$ Spinocerebellar ataxia (SCA) subtypes are often caused by expansions in non-coding regions of genes like $\textit {SCA8, SCA10, SCA12}$ and $\it {SCA36}$. Other ataxias are known to be associated with repeat expansions such as fragile X-associated tremor ataxia syndrome (FXTAS) or expansions in the $\it C9orf72$ gene. When no mutation has been identified in the aforementioned genes next-generation sequencing (NGS)-based diagnostics may also be applied. In order to define an optimal diagnostic strategy, more information about the frequency and phenotypic characteristics of rare repeat expansion disorders associated with ataxia should be at hand. $\textbf {Methods:}$ We analyzed a consecutive cohort of 440 German unrelated patients with symptoms of cerebellar ataxia, dysarthria and other unspecific symptoms who were referred to our center for SCA diagnostics. They showed alleles in the normal range for the most common SCA subtypes SCA1-3, SCA6, SCA7 and SCA17. These patients were screened for expansions causing SCA8, SCA10, SCA12, SCA36 and FXTAS as well as for the pathogenic hexanucleotide repeat in the $\it C9orf72$ gene. $\textbf {Results:}$ Expanded repeats for SCA10, SCA12 or SCA36 were not identified in the analyzed patients. Five patients showed expanded SCA8 CTA/CTG alleles with 92-129 repeats. One 51-year-old male with unclear dementia symptoms was diagnosed with a large GGGGCC repeat expansion in $\it C9orf72$. The analysis of the fragile X mental retardation 1 gene $\textit {(FMR1)}$ revealed one patient with a premutation (>50 CGG repeats) and seven patients with alleles in the grey zone (41 to 54 CGG repeats). $\textbf {Conclusions:}$ Altogether five patients showed 92 or more SCA8 CTA/CTG combined repeats. Our results support the assumption that smaller $\it FMR1$ gene expansions could be associated with the risk of developing neurological signs. The results do not support genetic testing for $\it C9orf72$ expansion in ataxia patients

Microscopic and biochemical hallmarks of BICD2\it BICD2-associated muscle pathology toward the evaluation of novel variants

$\it BICD2$ variants have been linked to neurodegenerative disorders like spinal muscular atrophy with lower extremity predominance (SMALED2) or hereditary spastic paraplegia (HSP). Recently, mutations in $\it BICD2$ were implicated in myopathies. Here, we present one patient with a known and six patients with novel $\it BICD2$ missense variants, further characterizing the molecular landscape of this heterogenous neurological disorder. A total of seven patients were genotyped and phenotyped. Skeletal muscle biopsies were analyzed by histology, electron microscopy, and protein profiling to define pathological hallmarks and pathogenicity markers with consecutive validation using fluorescence microscopy. Clinical and MRI-features revealed a typical pattern of distal paresis of the lower extremities as characteristic features of a $\it BICD2$-associated disorder. Histological evaluation showed myopathic features of varying severity including fiber size variation, lipofibromatosis, and fiber splittings. Proteomic analysis with subsequent fluorescence analysis revealed an altered abundance and localization of thrombospondin-4 and biglycan. Our combined clinical, histopathological, and proteomic approaches provide new insights into the pathophysiology of $\it BICD2$-associated disorders, confirming a primary muscle cell vulnerability. In this context, biglycan and thrombospondin-4 have been identified, may serve as tissue pathogenicity markers, and might be linked to perturbed protein secretion based on an impaired vesicular transportation

Exome sequencing and optical genome mapping in molecularly unsolved cases of duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a severe progressive muscle disease that mainly affects boys due to $\it X$-linked recessive inheritance. In most affected individuals, MLPA or sequencing-based techniques detect deletions, duplications, or point mutations in the dystrophin-encoding $\it DMD$ gene. However, in a small subset of patients clinically diagnosed with DMD, the molecular cause is not identified with these routine methods. Evaluation of the 60 DMD patients in our center revealed three cases without a known genetic cause. DNA samples of these patients were analyzed using whole-exome sequencing (WES) and, if unconclusive, optical genome mapping (OGM). WES led to a diagnosis in two cases: one patient was found to carry a splice mutation in the $\it DMD$ gene that had not been identified during previous Sanger sequencing. In the second patient, we detected two variants in the fukutin gene $\it (FKTN)$ that were presumed to be disease-causing. In the third patient, WES was unremarkable, but OGM identified an inversion disrupting the $\it DMD$ gene (~1.28 Mb) that was subsequently confirmed with long-read sequencing. These results highlight the importance of reanalyzing unsolved cases using WES and demonstrate that OGM is a useful method for identifying large structural variants in cases with unremarkable exome sequencing