TRAPPC11-CDG muscular dystrophy: Review of 54 cases including a novel patient.

The trafficking protein particle (TRAPP) complex is a multisubunit protein complex that functions as a tethering factor involved in intracellular trafficking. TRAPPC11, a crucial subunit of this complex, is associated with pathogenic variants that cause a spectrum of disease, which can range from a limb girdle muscular dystrophy (LGMD) to developmental disability with muscle disease, movement disorder and global developmental delay (GDD)/intellectual disability (ID), or even a congenital muscular dystrophy (CMD). We reviewed the phenotype of all reported individuals with TRAPPC11-opathies, including an additional Mexican patient with novel compound heterozygous missense variants in TRAPPC11 (c.751 T > C and c.1058C > G), restricted to the Latino population. In these 54 patients muscular dystrophy signs are common (early onset muscle weakness, increased serum creatine kinase levels, and dystrophic changes in muscle biopsy). They present two main phenotypes, one with a slowly progressive LGMD with or without GDD/ID (n = 12), and another with systemic involvement characterized by short stature, GDD/ID, microcephaly, hypotonia, poor speech, seizures, cerebral atrophy, cerebellar abnormalities, movement disorder, scoliosis, liver disease, and cataracts (n = 42). In 6 of them CMD was identified. Obstructive hydrocephaly, retrocerebellar cyst, and talipes equinovarus found in the individual reported here has not been described in TRAPPC11 deficiency. As in previous patients, membrane trafficking assays in our patient showed defective abnormal endoplasmic reticulum-Golgi transport as well as decreased expression of LAMP2, and ICAM-1 glycoproteins. This supports previous statements that TRAPPC11-opathies are in fact a congenital disorder of glycosylation (CDG) with muscular dystrophy.

Corrigendum: ALG1-CDG Caused by Non-Functional Alternative Splicing Involving a Novel Pathogenic Complex Allele.

[This corrects the article DOI: 10.3389/fgene.2021.744884.].

ALG1-CDG Caused by Non-functional Alternative Splicing Involving a Novel Pathogenic Complex Allele.

This study reports on a Mexican mestizo patient with a multi-systemic syndrome including neurological involvement and a type I serum transferrin profile. Clinical exome sequencing revealed complex alleles in ALG1, the encoding gene for the chitobiosyldiphosphodolichol beta-mannosyltransferase that participates in the formation of the dolichol-pyrophosphate-GlcNAc2Man5, a lipid-linked glycan intermediate during N-glycan synthesis. The identified complex alleles were NM_019109.5(ALG1): c.[208 + 16_208 + 19dup; 208 + 25G > T] and NM_019109.5(ALG1): c.[208 + 16_208 + 19dup; 1312C > T]. Although both alleles carried the benign variant c.208 + 16_208 + 19dup, one allele carried a known ALG1 pathogenic variant (c.1312C > T), while the other carried a new uncharacterized variant (c.208 + 25G > T) causing non-functional alternative splicing that, in conjunction with the benign variant, defines the pathogenic protein effect (p.N70S_S71ins9). The presence in the patient's serum of the pathognomonic N-linked mannose-deprived tetrasaccharide marker for ALG1-CDG (Neu5Acα2,6Galß1,4-GlcNAcß1,4GlcNAc) further supported this diagnosis. This is the first report of an ALG1-CDG patient from Latin America.