Familial hypercholanemia (FHC) is characterized by elevated serum bile acid concentrations, itching, and fat malabsorption. We show here that FHC in Amish individuals is associated with mutations in tight junction protein 2 (encoded by TJP2, also known as ZO-2) and bile acid Coenzyme A: amino acid N-acyltransferase (encoded by BAAT). The mutation of TJP2, which occurs in the first PDZ domain, reduces domain stability and ligand binding in vitro. We noted a morphological change in hepatic tight junctions. The mutation of BAAT, a bile acid-conjugating enzyme, abrogates enzyme activity; serum of individuals homozygous with respect to this mutation contains only unconjugated bile acids. Mutations in both TJP2 and BAAT may disrupt bile acid transport and circulation. Inheritance seems to be oligogenic, with genotype at BAAT modifying penetrance in individuals homozygous with respect to the mutation in TJP2.
- Cardiac System
- Clinical Case Report
- Diagnostic Development
- Disease Discovery
- Endocrine System
- Genomic Testing
- Hepatic System
- Immune System
- Natural History
- Neurologic System
- Ocular System
- Population Genetics
- Public Health
- Renal System
- Skeletal System
The primary goal of our research will always be to find effective and affordable treatments for patients. Over the years, we have shared our methods and discoveries with the broader scientific community.
In the over 30 years since the Clinic's founding, our staff have published more than 120 peer-reviewed research papers, fueled by close collaboration between our clinical and laboratory teams and effective relationships with academic, scientific, and clinical partners.
Authors: Kelley RI, Robinson D, Puffenberger EG, Strauss KA, Morton DH
A new metabolic disorder characterized by severe congenital microcephaly, death within the first year, and severe 2-ketoglutaric aciduria has been found among the Old-Order Amish of Lancaster County, Pennsylvania. Amish lethal microcephaly segregates as an autosomal recessive disorder and has an unusually high incidence of at least 1 in 500 births. When the infants are well, the urine organic acid profiles show isolated, extreme elevations of 2-ketoglutaric acid. However, during otherwise simple viral illnesses, the infants often develop a metabolic acidosis, which may follow a lethal course. Cranial magnetic resonance imaging of a single patient showed a smooth, immature brain similar to that of a 20-week fetus except for a moderate degree of cerebellar vermal hypoplasia. Assay of 2-ketoglutarate dehydrogenase in cultured lymphoblasts of one patient showed normal activity. Amish lethal microcephaly maps to 17q25 and may be caused by a defect in a mitochondrial inner membrane protein functioning as a 2-ketoglutarate transporter.
Authors: Rosenberg MJ, Agarwala R, Bouffard G, Davis J, Fiermonte G, Hilliard MS, Koch T, Kalikin LM, Makalowska I, Morton DH, Petty EM, Weber JL, Palmieri F, Kelley RI, SchÃ¤ffer AA, Biesecker LG
The disorder Amish microcephaly (MCPHA) is characterized by severe congenital microcephaly, elevated levels of alpha-ketoglutarate in the urine and premature death. The disorder is inherited in an autosomal recessive pattern and has been observed only in Old Order Amish families whose ancestors lived in Lancaster County, Pennsylvania. Here we show, by using a genealogy database and automated pedigree software, that 23 nuclear families affected with MCPHA are connected to a single ancestral couple. Through a whole-genome scan, fine mapping and haplotype analysis, we localized the gene affected in MCPHA to a region of 3 cM, or 2 Mb, on chromosome 17q25. We constructed a map of contiguous genomic clones spanning this region. One of the genes in this region, SLC25A19, which encodes a nuclear mitochondrial deoxynucleotide carrier (DNC), contains a substitution that segregates with the disease in affected individuals and alters an amino acid that is highly conserved in similar proteins. Functional analysis shows that the mutant DNC protein lacks the normal transport activity, implying that failed deoxynucleotide transport across the inner mitochondrial membrane causes MCPHA. Our data indicate that mitochondrial deoxynucleotide transport may be essential for prenatal brain growth.
Authors: Morton DH, Strauss KA, Robinson DL, Puffenberger EG, Kelley RI
To evaluate an approach to the diagnosis and treatment of maple syrup disease (MSD).
Authors: Kalsner LR, Rohr FJ, Strauss KA, Korson MS, Levy HL
Tyrosine supplementation has not consistently been found to improve neuropsychologic function in phenylketonuria (PKU), possibly because of failure to achieve adequate levels of tyrosine in the brain.
Authors: M. Esther Gallardo, Lourdes R. Desviat, José M. Rodríguez, Jorge Esparza-Gordillo, Celia Pérez-Cerdá, Belén Pérez, Pilar Rodríguez-Pombo, Olga Criado, Raul Sanz, D. Holmes Morton, K. Michael Gibson, Thuy P. Le, Antonia Ribes, Santiago Rodríguez de Córdoba, Magdalena Ugarte, and Miguel Á. Peñalva
3-Methylcrotonylglycinuria is an inborn error of leucine catabolism and has a recessive pattern of inheritance that results from the deficiency of 3-methylcrotonyl-CoA carboxylase (MCC). The introduction of tandem mass spectrometry in newborn screening has revealed an unexpectedly high incidence of this disorder, which, in certain areas, appears to be the most frequent organic aciduria. MCC, an heteromeric enzyme consisting of α (biotin-containing) and β subunits, is the only one of the four biotin-dependent carboxylases known in humans that has genes that have not yet been characterized, precluding molecular studies of this disease. Here we report the characterization, at the genomic level and at the cDNA level, of both the MCCA gene and the MCCB gene, encoding the MCCα and MCCβ subunits, respectively. The 19-exon MCCA gene maps to 3q25-27 and encodes a 725-residue protein with a biotin attachment site; the 17-exon MCCB gene maps to 5q12-q13 and encodes a 563-residue polypeptide. We show that disease-causing mutations can be classified into two complementation groups, denoted “CGA” and “CGB.” We detected two MCCA missense mutations in CGA patients, one of which leads to absence of biotinylated MCCα. Two MCCB missense mutations and one splicing defect mutation leading to early MCCβ truncation were found in CGB patients. A fourth MCCB mutation also leading to early MCCβ truncation was found in two nonclassified patients. A fungal model carrying an mccA null allele has been constructed and was used to demonstrate, in vivo, the involvement of MCC in leucine catabolism. These results establish that 3-methylcrotonylglycinuria results from loss-of-function mutations in the genes encoding the α and β subunits of MCC and complete the genetic characterization of the four human biotin-dependent carboxylases.
Authors: Johnston JJ, Kelley RI, Crawford TO, Morton DH, Agarwala R, Koch T, Schaeffer AA, Francomano CA, Biesecker LG
The nemaline myopathies are characterized by weakness and eosinophilic, rodlike (nemaline) inclusions in muscle fibers. Amish nemaline myopathy is a form of nemaline myopathy common among the Old Order Amish. In the first months of life, affected infants have tremors with hypotonia and mild contractures of the shoulders and hips. Progressive worsening of the proximal contractures, weakness, and a pectus carinatum deformity develop before the children die of respiratory insufficiency, usually in the second year. The disorder has an incidence of ∼1 in 500 among the Amish, and it is inherited in an autosomal recessive pattern. Using a genealogy database, automated pedigree software, and linkage analysis of DNA samples from four sibships, we identified an ∼2-cM interval on chromosome 19q13.4 that was homozygous in all affected individuals. The gene for the sarcomeric thin-filament protein, slow skeletal muscle troponin T (TNNT1), maps to this interval and was sequenced. We identified a stop codon in exon 11, predicted to truncate the protein at amino acid 179, which segregates with the disease. We conclude that Amish nemaline myopathy is a distinct, heritable, myopathic disorder caused by a mutation in TNNT1.
Authors: Morton DH, Salen G, Batta AK, Shefer S, Tint GS, Belchis D, Shneider B, Puffenberger E, Bull L, Knisely AS
The mechanism for abnormal hepatic bile acid transport was investigated in an 18-month-old Amish boy who presented with pruritus, poor growth, and severe bleeding episodes. Serum bilirubin, gamma-glutamyltranspeptidase, and cholesterol levels were normal, but prothrombin time and partial thromboplastin time were prolonged and bone alkaline phosphatase level was elevated.
Help us to continue to provide patients with timely, affordable and effective care!
Our clinic serves as a trusted medical home for families working to prevent and treat genetic illness in their children. Serving predominantly Amish and Mennonite families, the sturdy, timber-framed building was "raised" by the hands of those in the Anabaptist community outside of Strasburg, PA. Inside the clinic is filled with an array of high-tech gene sequencing that allows us to deliver state of the art care in a nurturing environment.