The GALT rush: high carrier frequency of an unusual deletion mutation of the GALT gene in the Ashkenazi population

Classic galactosemia is an autosomal recessive disorder of galactose metabolism manifesting in the first weeks of life following exposure to a milk-based diet. Despite the benefit of avoidance of lactose, many patients suffer from long-term complications including neurological deficits and ovarian failure. To date, over 230 mutations have been described in the GALT gene resulting in galactosemia. Recently, an unusual mutation was characterized causing a 5.5 kb deletion, with a relatively high carrier rate in subjects of Ashkenazi Jewish (AJ) descent. The aim of this study was to estimate the carrier frequency of this mutation in the AJ population in Israel. For this purpose we developed a high-throughput methodology to genotype both normal and deleted alleles using a chip-based matrix-assisted laser desorption-time-of-flight (MALDI-TOF) mass spectrometer and Multiplex PCR. DNA samples of 760 anonymous AJ subjects were submitted for analysis, subsequently detecting six individuals heterozygous for the GALT deletion mutation, giving a carrier frequency of 1 in 127 (0.79%). Based on these results, we suggest that the method described here provides a basis for genetic screening and prenatal counseling and can potentially reduce the morbidity and mortality associated with delayed diagnosis of galactosemia in this patient population.

Different patterns of human serum procollagen C-proteinase enhancer1 (PCPE1)

BACKGROUND

Procollagen C-proteinase (PCP) enhancer 1 (PCPE1) specifically stimulates the PCP activity of bone morphogenic protein 1 (BMP1), a multisubstrate enzyme essential to the formation of extracellular matrix, via direct interaction with its substrate procollagen. Thus, in this study we sought to determine if serum PCPE1 (sPCPE1), a regulator of collagen formation, can be used as a diagnostic marker of collagen metabolism/remodeling.

METHODS

We developed a method to track sPCPE1, and the findings were applied to evaluate the association of sPCPE1 glycopatterns with growth and presence of bone complication.

RESULTS

Isoelectric focusing revealed that sPCPE1 has a multi-band appearance and that sPCPE1 glycopatterns are due to an N-linked oligosaccharide decorated with sialic acid. Evaluation of PCPE1 glycopatterns in different groups of subjects revealed a significant difference among preterm babies, term babies, and adults. Furthermore, in adults with breast cancer, the glycopattern intensity correlated with the presence of bone metastasis.

CONCLUSIONS

The sPCPE1 glycopattern appears to be associated with the physiological and pathological states of bone. This study shows for the first time sPCPE1 glycopattern and suggest that changes in glycosylation of the protein may be in correlation with collagen metabolism. Studies are currently underway to determine its appearance in the serum of normal population on one hand and its appearance during growth and metabolic bone diseases on the other hand.

Genotype-phenotype correlations analysis of mutations in the phenylalanine hydroxylase (PAH) gene

The aims of our research were to define the genotype-phenotype correlations of mutations in the phenylalanine hydroxylase (PAH) gene that cause phenylketonuria (PKU) among the Israeli population. The mutation spectrum of the PAH gene in PKU patients in Israel is described, along with a discussion on genotype-phenotype correlations. By using polymerase chain reaction/denaturing high-performance liquid chromatography (PCR/dHPLC) and DNA sequencing, we screened all exons of the PAH gene in 180 unrelated patients with four different PKU phenotypes [classic PKU, moderate PKU, mild PKU, and mild hyperphenylalaninemia (MHP)]. In 63.2% of patient genotypes, the metabolic phenotype could be predicted, though evidence is also found for both phenotypic inconsistencies among subjects with more than one type of mutation in the PAH gene. Data analysis revealed that about 25% of patients could participate in the future in (6R)-L: -erythro-5, 6, 7, 8-tetrahydrobiopterin (BH4) treatment trials according to their mutation genotypes. This study enables us to construct a national database in Israel that will serve as a valuable tool for genetic counseling and a prognostic evaluation of future cases of PKU.