Bleeding and Platelet Disorders

Gene: BLOC1S5

Green List (high evidence)

2 unrelated patients with mild oculocutaneous albinism, moderate bleeding diathesis, platelet aggregation deficit, and a dramatically decreased number of platelet dense granules, all signs compatible with HPS. Identified distinct homozygous variants in the BLOC1S5 gene (patient 1: deletion of exons 3 and 4, patient 2: 1-bp deletion in exon 4). Parental segregation confirmatory in patient 1, quantitative PCR analysis confirmatory in patient 2). Functional tests performed on platelets of one patient displayed an absence of the obligate multisubunit complex BLOC-1, showing that the variant disrupts BLOC1S5 function and impairs BLOC-1 assembly. Expression of the patient-derived BLOC1S5 deletion in nonpigmented murine Bloc1s5-/- melan-mu melanocytes failed to rescue pigmentation, the assembly of a functional BLOC-1 complex, and melanosome cargo trafficking, unlike the wild-type allele. Pathogenic variants in the genes encoding three other BLOC-1 subunits (DTNBP1, BLOC1S3, and BLOC1S6) underlie HPS types 7, 8, and 9 respectively.
Sources: Literature

Created: 30 Sep 2020, 8:22 a.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Hermansky–Pudlak syndrome 11, MIM#619172

Publications

• 32565547

Green List (high evidence)

2 unrelated patients with mild oculocutaneous albinism, moderate bleeding diathesis, platelet aggregation deficit, and a dramatically decreased number of platelet dense granules, all signs compatible with HPS. Identified distinct homozygous variants in the BLOC1S5 gene (patient 1: deletion of exons 3 and 4, patient 2: 1-bp deletion in exon 4). Parental segregation confirmatory in patient 1, quantitative PCR analysis confirmatory in patient 2).

Functional tests performed on platelets of one patient displayed an absence of the obligate multisubunit complex BLOC-1, showing that the variant disrupts BLOC1S5 function and impairs BLOC-1 assembly. Expression of the patient-derived BLOC1S5 deletion in nonpigmented murine Bloc1s5-/- melan-mu melanocytes failed to rescue pigmentation, the assembly of a functional BLOC-1 complex, and melanosome cargo trafficking, unlike the wild-type allele.

Pathogenic variants in the genes encoding three other BLOC-1 subunits (DTNBP1, BLOC1S3, and BLOC1S6) underlie HPS types 7, 8, and 9 respectively.
Sources: Literature

Created: 30 Sep 2020, 4:05 a.m.

Mode of inheritance
BIALLELIC, autosomal or pseudoautosomal

Phenotypes
Hermansky–Pudlak syndrome type 11, no OMIM#

Publications

• PMID: 32565547

Variants in this GENE are reported as part of current diagnostic practice