Our research is directed toward identifying, understanding and reversing the consequences of gene mutations on protein and cell function in inherited human disease. Cell biological and molecular genetic approaches are used in conjunction with clinical studies to obtain a better understanding of gene expression and the molecular pathophysiology underlying selected Mendelian and complex trait diseases. To accomplish this objective, we study gene variation and function in unique human genetic isolates, inbred animal models and families with inherited developmental disorders. Research projects reflect a “bench to bedside” approach, combining efforts from interdisciplinary investigations on humans and animal models. Current study areas include the link between Gaucher disease and parkinsonism, development of novel gene and replacement therapies for Gaucher disease, and the genetics of selected psychiatric disorders, including bipolar affective disorder in the Old Order Amish and obsessive compulsive disorder in domestic animals. 

Gaucher Disease Therapy

This research area focusus on the development of new oral biologics for treating Gaucher Disease. Gaucher Disease a lysosomal storage disorder caused by inherited deficiencies of the enzyme glucocerebrosidase (GBA). Decreases in functioning GBA levels lead to lipid accumulation in the spleen, liver, brain and bone marrow that cause a wide range of clinical manifestations. There are 3 different types of this disease based on the presence or absence of early onset brain involvement. Type 1 is the most common form of Gaucher disease with no neuropathic phenotypes and accounts for more than 90% of all cases. Type 2 is rare and involves severe neurological (brain stem) abnormalities. It is usually fatal within the first 2 years, and it is currently untreatable because of the severe, irreversible brain damage. Type 3 shows similar symptoms as type 1 as well as neurological involvement.

Currently, available treatments for Gaucher disease include enzyme replacement (ERT) and substrate reduction therapies. ERT involves receiving intravenous (IV) infusions about every 2 weeks and can cost up to $200,000 or more each year.

This research will use orally administered glucan particles containing DNA to produce increased levels of functioning GBA. Success of the treatments will be determined by following GBA levels and biomarkers in various tissues of the mice during treatment. An increase in GBA should also lead to a decrease in the lipid glucocerebroside (GL1) and glucosylsphingosine (lyso-GL1).

Gaucher Disease Linked Parkinsons

We are using mouse models of Gaucher disesase to (i) identify novel molecular abnormalities impacting pathophysiology of  Gaucher related PD and sporadic PD, (ii) carry out longitudinal studies of PD progression and biomarker discovery, and (iii) enable testing of novel strategies for treatment, intervention, and potentially even prevention of Gaucher disease and Parkinsons.

Recent clinical, epidemiological and experimental studies have confirmed a strong connection between Parkinson’s disease (PD) and individuals carrying a glucocerebrosidase gene (GBA) Gaucher mutation.  We are building upon our published in-vivo findings of altered nigrostriatal pathway dopaminergic neurotransmission in the conduritol-beta-epoxide (CBE) pharmacological Gaucher mouse model of reduced GBA enzyme activity.  This is the first description in an animal model to recapitulate the synaptic dysfunction reported in human striatal imaging studies of Gaucher mutation carriers asymptomatic for Parkinsonism.  CBE administration produced markedly reduced evoked dopamine release and post-synaptic density size.  These synaptic abnormalities were accompanied by robust elevation of neuroinflammatory markers and alpha-synuclein (a-syn) in nigrostriatal tissue.  To further address the unmet need for better understanding and treatment of bone and brain involvement in Gaucher disease, and more specifically as models for the study of Gaucher-related Parkinsonism and sporadic Parkinson’s disease, we are using two long-lived transgenic mouse models of Gaucher disease bearing the L444P or the R463C point mutations frequently found in Gaucher patients.  These aged homozygous Gaucher transgenic mutant mice have a lifespan of from 1-2 years and show abnormal a-syn accumulation and astroglial activation in the striatum.

Potential Rotation Projects

Development of an Osteoprotegerin Gene Therapy to Increase Bone Density

An orally administered gene therapy using macrophage targeted yeast cell wall particles containing DNA encoding human osteoprotegerin, OPG, is being developed to increase bone density and quality by reducing the extent of osteoclast mediated bone resorption. Low bone mass such as osteoporosis is a major health risk for millions of women and men, predisposing individuals to bone fractures, as well as sequelae including stroke and an accelerated decrease in quality of life. Administration of OPG improves the clinical manifestations of bone loss, but current formulations of OPG proteins must be recombinantly produced and intravenously administered. It is anticipated that the improved delivery of OPG to macrophages and osteoclasts in bone by this gene therapy approach will produce increased bone density as a result of reduced bone resorption. The proposed studies will assess the in-vivo impact of this therapeutic approach to improve the skeletal manifestations of low bone density and excessive bone resorption.

Development of an Orally Administered Gene Therapy for Gaucher Disease

An orally administered gene therapy is being been developed as a next generation therapeutic to restore normal enzymatic activity in Gaucher disease, the most common lysosomal storage disorder. This approach uses yeast cell wall particles containing DNA or RNA encoding human glucocerebrosidase to restore normal enzyme in-vivo in Gaucher mice. The skeletal and central nervous system complications of Gaucher disease still present an enormous challenge for current enzyme and gene replacement therapies. Despite the successes of gene therapy strategies in animal models, the clinical trials conducted to date have generally resulted in low levels of gene expression. Studies will determine the extent of improvement in enzyme levels in macrophages and tissues of treated Gaucher mice, the extent of reversal of lipid storage and tissue pathology and impact on survival. We anticipate that this approach will provide improved delivery of human glucocerebrosidase to many tissues, including bone. If macrophages containing human glucocerebrosidase migrate into brain, the resulting increased enzyme levels could provide clinical benefit for the neurological manifestations of Gaucher disease. The successful development of this therapeutic strategy should provide a safer, more efficient and cost effective treatment for patients with Gaucher disease, as well as providing a prototype of therapy to benefit those having a wide range of other lysosomal diseases.

Identification of Gene Mutations Causing Human Disease

Genetic studies are carried out to obtain a better understanding of the molecular basis of human diseases by identifying correlations between molecular variations and clinical manifestations. Examples of clinical research projects with molecular components include: psychiatric disorders (manic-depressive illness; schizophrenia); Gaucher disease and other inherited metabolic disorders; and, Ellis van-Creveld dwarfism.