The adult polyglucosan body disease mutation GBE1 c.1076A>C occurs at high frequency in persons of Ashkenazi Jewish background.

Mutations of the glycogen branching enzyme gene, GBE1, result in glycogen storage disease (GSD) type IV, an autosomal recessive disorder having multiple clinical forms. One mutant allele of this gene, GBE1 c.1076A>C, has been reported in Ashkenazi Jewish cases of an adult-onset form of GSD type IV, adult polyglucosan body disease (APBD), but no epidemiological analyses of this mutation have been performed. We report here the first epidemiological study of this mutation in persons of Ashkenazi Jewish background and find that this mutation has a gene frequency of 1 in 34.5 (95% CI: 0.0145-0.0512), similar to the frequency of the common mutation causing Tay-Sachs disease among Ashkenazi Jews. This finding reveals APBD to be another monogenic disorder that occurs with increased frequency in persons of Ashkenazi Jewish ancestry.

Hyaluronidase 1 and ß-hexosaminidase have redundant functions in hyaluronan and chondroitin sulfate degradation.

Hyaluronan (HA), a member of the glycosaminoglycan (GAG) family, is a critical component of the extracellular matrix. A model for HA degradation that invokes the activity of both hyaluronidases and exoglycosidases has been advanced. However, no in vivo studies have been done to determine the extent to which these enzymes contribute to HA breakdown. Herein, we used mouse models to investigate the contributions of the endoglycosidase HYAL1 and the exoglycosidase ß-hexosaminidase to the lysosomal degradation of HA. We employed histochemistry and fluorophore-assisted carbohydrate electrophoresis to determine the degree of HA accumulation in mice deficient in one or both enzyme activities. Global HA accumulation was present in mice deficient in both enzymes, with the highest levels found in the lymph node and liver. Chondroitin, a GAG similar in structure to HA, also broadly accumulated in mice deficient in both enzymes. Accumulation of chondroitin sulfate derivatives was detected in mice deficient in both enzymes, as well as in ß-hexosaminidase-deficient mice, indicating that both enzymes play a significant role in chondroitin sulfate breakdown. Extensive accumulation of HA and chondroitin when both enzymes are lacking was not observed in mice deficient in only one of these enzymes, suggesting that HYAL1 and ß-hexosaminidase are functionally redundant in HA and chondroitin breakdown. Furthermore, accumulation of sulfated chondroitin in tissues provides in vivo evidence that both HYAL1 and ß-hexosaminidase cleave chondroitin sulfate, but it is a preferred substrate for ß-hexosaminidase. These studies provide in vivo evidence to support and extend existing knowledge of GAG breakdown.

Hyal-1 but not Hyal-3 deficiency has an impact on ovarian folliculogenesis and female fertility by altering the follistatin/activin/Smad3 pathway and the apoptotic process.

Ovarian follicle development is a process regulated by various endocrine, paracrine and autocrine factors that act coordinately to promote follicle growth. However, the vast majority of follicles does not reach the pre-ovulatory stage but instead, undergo atresia by apoptosis. We have recently described a role for the somatic hyaluronidases (Hyal-1, Hyal-2, and Hyal-3) in ovarian follicular atresia and induction of granulosa cell apoptosis. Herein, we show that Hyal-1 but not Hyal-3 null mice have decreased apoptotic granulosa cells after the induction of atresia and an increased number of retrieved oocytes after stimulation of ovulation. Furthermore, young Hyal-1 null mice had a significantly higher number of primordial follicles than age matched wild-type animals. Recruitment of these follicles at puberty resulted in an increased number of primary and healthy preantral follicles in Hyal-1 null mice. Consequently, older Hyal-1 deficient female mice have prolonged fertility. At the molecular level, immature Hyal-1 null mice have decreased mRNA expression of follistatin and higher levels of phospho-Smad3 protein, resulting in increased levels of phospho-Akt in pubertal mice. Hyal-1 null ovarian follicles did not exhibit hyaluronan accumulation. For Hyal-3 null mice, compensation by Hyal-1 or Hyal-2 might be related to the lack of an ovarian phenotype. In conclusion, our results demonstrate that Hyal-1 plays a key role in the early phases of folliculogenesis by negatively regulating ovarian follicle growth and survival. Our findings add Hyal-1 as an ovarian regulator factor for follicle development, showing for the first time an interrelationship between this enzyme and the follistatin/activin/Smad3 pathway.

A complete deficiency of Hyaluronoglucosaminidase 1 (HYAL1) presenting as familial juvenile idiopathic arthritis.

We describe a single consanguineous family with three affected children exhibiting knee and/or hip pain associated with swelling. Detailed clinical evaluation demonstrated diffuse joint involvement with an unusual proliferative synovitis on MRI. Synovial biopsies were notable for an infiltration of macrophages with abundant cytoplasm filled with faintly basophilic vacuoles. We used homozygosity mapping with a panel of 262,000 single nucleotide polymorphism markers to identify a homozygous stretch of 40.52 Mb on chromosome 3p22.3 - 3p13 that segregated with the arthropathy in the family. Of the 378 genes in the interval, the three hyaluronoglucosaminidase genes were considered good candidates based on the phenotype. Dideoxy sequencing identified a homozygous deletion in HYAL1, c.104delT, resulting in a premature termination codon, p.Val35AlafsX25, found in all three affected children. Enzymatic analysis confirmed total HYAL1 deficiency in the three affected children. This confirms the diagnosis of Mucopolysaccharidosis IX (MPS IX) which has only been described in a single patient to date. In contrast to the previously described MPS IX patient, our three patients display a phenotype limited to the joints, suggesting that this is the primary manifestation of HYAL1 deficiency.