The diagnostic gap for rare neurodegenerative diseases is still considerable, despite continuous advances in gene identification. Many novel Mendelian genes have only been identified in a few families worldwide. Here we report the identification of an autosomal-dominant gene for hereditary spastic paraplegia (HSP) in 10 families that are of diverse geographic origin and whose affected members all carry unique truncating changes in a circumscript region of UBAP1 (ubiquitin-associated protein 1). HSP is a neurodegenerative disease characterized by progressive lower-limb spasticity and weakness, as well as frequent bladder dysfunction. At least 40% of affected persons are currently undiagnosed after exome sequencing. We identified pathological truncating variants in UBAP1 in affected persons from Iran, USA, Germany, Canada, Spain, and Bulgarian Roma. The genetic support ranges from linkage in the largest family (LOD ¼ 8.3) to three confirmed de novo mutations. We show that mRNA in the fibroblasts of affected individuals escapes nonsense-mediated decay and thus leads to the expression of truncated proteins; in addition, concentrations of the full-length protein are reduced in comparison to those in controls. This suggests either a dominant-negative effect or haploinsufficiency. UBAP1 links endosomal trafficking to the ubiquitination machinery pathways that have been previously implicated in HSPs, and UBAP1 provides a bridge toward a more unified pathophysiology.

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Pathogenic variants in the Golgi localised alpha 1,6 fucosyltransferase, FUT8, cause a rare inherited metabolic disorder known as FUT8‐CDG. To date, only three affected individuals have been reported presenting with a constellation of symptoms including intrauterine growth restriction, severe delays in growth and development, other neurological impairments, significantly shortened limbs, respiratory complications, and shortened lifespan. Here, we report an additional four unrelated affected individuals homozygous for novel pathogenic variants in FUT8. Analysis of serum N‐glycans revealed a complete lack of core fucosylation, an important diagnostic biomarker of FUT8‐CDG. Our data expands both the molecular and clinical phenotypes of FUT8‐CDG and highlights the importance of identifying a reliable biomarker for confirming potentially pathogenic variants.

Autosomal recessive spastic ataxia of Charlevoix–Saguenay (ARSACS) is a rare neurodegenerative disorder caused by biallelic mutations in the SACS gene. Once thought to be limited to Charlevoix–Saguenay region of Quebec, recent evidence has indicated that this disorder is present worldwide. It is classically characterized by the triad of ataxia, pyramidal involvement, and axonal-demyelinating sensorimotor neuropathy. However, diverse clinical features have been reported to be associated with this disorder. In this report, we present the first Iranian family affected by ARSACS with unique clinical features (mirror movements, hypokinesia/bradykinesia, and rigidity) harboring a novel deletion mutation in the SACS gene. Our findings expand the genetic and phenotypic spectrum of this disorder.

BackgroundWiskott-Aldrich syndrome is an X-linked recessive immunodeficiency due to mutations in Wiskott-Aldrich syndrome (WAS) gene. WAS gene is encoded for a multifunctional protein with key roles in actin polymerization, signaling pathways, and cytoskeletal rearrangement. Therefore, the impaired protein or its absence cause phenotypic spectrum of the disease. Since identification of novel mutations in WAS gene can help uncover the exact pathogenesis of Wiskott-Aldrich syndrome, the purpose of this study was to investigate disease causing-mutation in an Iranian male infant suspicious of this disorder.Case presentationThe patient had persistent thrombocytopenia from birth, sepsis, and recurrent gastrointestinal bleeding suggestive of both Wiskott-Aldrich syndrome and chronic colitis in favor of inflammatory bowel disease (IBD). To find mutated gene in the proband, whole exome sequencing was performed for the patient and its data showed a novel, private, hemizygous splice site mutation in WAS gene (c.360 + 1G > C).ConclusionsOur study found a novel, splice-site mutation in WAS gene and help consider the genetic counselling more precisely for families with clinical phenotypes of both Wiskott-Aldrich syndrome and inflammatory bowel disease and may suggest linked pathways between these two diseases.