Assessment of plasma lyso-Gb(3)for clinical monitoring of treatment response in migalastat-treated patients with Fabry disease

Purpose To assess the utility of globotriaosylsphingosine (lyso-Gb(3)) for clinical monitoring of treatment response in patients with Fabry disease receiving migalastat. Methods A post hoc analysis evaluated data from 97 treatment-naive and enzyme replacement therapy (ERT)-experienced patients with migalastat-amenableGLAvariants from FACETS (NCT00925301) and ATTRACT (NCT01218659) and subsequent open-label extension studies. The relationship between plasma lyso-Gb(3)and measures of Fabry disease progression (left ventricular mass index [LVMi], estimated glomerular filtration rate [eGFR], and pain) and the relationship between lyso-Gb(3)and incidence of Fabry-associated clinical events (FACEs) were assessed in both groups. The relationship between changes in lyso-Gb(3)and kidney interstitial capillary (KIC) globotriaosylceramide (Gb(3)) inclusions was assessed in treatment-naive patients. Results No significant correlations were identified between changes in lyso-Gb(3)and changes in LVMi, eGFR, or pain. Neither baseline lyso-Gb(3)levels nor the rate of change in lyso-Gb(3)levels during treatment predicted FACE occurrences in all patients or those receiving migalastat for >= 24 months. Changes in lyso-Gb(3)correlated with changes in KIC Gb(3)inclusions in treatment-naive patients. Conclusions Although used as a pharmacodynamic biomarker in research and clinical studies, plasma lyso-Gb(3)may not be a suitable biomarker for monitoring treatment response in migalastat-treated patients.Medical Biochemistr

Lyso-Gb3 is not a predictive biomarker of treatment response in migalastat-treated patients with migalastat-amenable variants

Medical Biochemistr

Consequences of aquaporin 2 tetramerization for genetics and routing

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An AQP2 mutant encoded in dominantly-inherited nephrogenic diabetes insipidus is impaired in its routing from a post-endoplasmic reticulum compartment

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Two novel mutations in the aquaporin-2 and the vasopressin V2 receptor genes in patients with congenital nephrogenic diabetes insipidus

The vasopressin V2 receptor (V2R) and the aquaporin-2 genes of two unrelated male patients with congenital nephrogenic diabetes insipidus were analyzed. The V2R gene of the patient of family 1 had the wild-type sequence. Consequently, the coding region of the aquaporin-2 gene including the exon-intron junctions was sequenced. A novel G to T transversion at codon 202, predictive of an exchange of tryptophan 202 by cysteine, was identified. As the mutation occurs at G-1 of the 5' splice donor site of intron 3, aberrant splicing is also likely. The mutation involves one of the supposed water pore-forming loops. Therefore, both aberrant splicing and amino acid substitution are likely to result in a functionally defective protein. Sequencing of the complete V2R gene of the male patient of family 2 revealed a novel single-base deletion at codon 310 (delta C1001), shifting the reading frame to give an altered amino acid sequence beginning at codon 311. The mutation is unique in predicting a C-terminally extended protein (termination after codon 434 in the mutant receptor instead of codon 371 in the wild-type). The deduced mutant protein is likely to be nonfunctional since the amino acid sequence of the seventh transmembrane domain and the C-terminus is altered

Molecular identification of the gene responsible for congenital nephrogenic diabetes insipidus

Antidiuretic hormone (arginine vasopressin) binds to and activates V2 receptors in renal collecting tubule cells. Subsequent stimulation of the Gs/adenylyl cyclase system promotes insertion of water pores into the luminal membrane and thereby reabsorption of fluid. In congenital nephrogenic diabetes insipidus (CNDI), an X-linked recessive disorder, the kidney fails to respond to arginine vasopressin. Here we report that an affected male of a family with CNDI has a deletion in the open reading frame of the V2 receptor gene, causing a frame shift and premature termination of translation in the third intracellular loop of the receptor protein. A normal receptor gene was found in the patient's brother. Both the normal and the mutant allele were detected in his mother. A different mutation, causing a codon change in the third transmembrane domain of the V2 receptor, was found in the open reading frame of an affected male but not in the unaffected brother belonging to another family suffering from CNDI