Recurrent De Novo Mutations Affecting Residue Arg138 of Pyrroline-5-Carboxylate Synthase Cause a Progeroid Form of Autosomal-Dominant Cutis Laxa

A de novo 1q23.3-q24.2 deletion combined with a GORAB missense mutation causes a distinctive phenotype with cutis laxa

Gerodermia osteodysplastica is a recessive segmental progeroid disorder mainly characterized by wrinkled skin, generalized connective tissue weakness, infantile onset osteoporosis and normal intelligence. Coding mutations in GORAB, localized on chromosome 1q24.2, are the cause of this disease. 1q24 deletions underlie a spectrum of disorders with intellectual disability and ear abnormalities as phenotypic hallmarks. Here we report on an individual from Azerbaijan originating from a non-consanguineous couple showing short stature, cutis laxa, frequent fractures, facial dysmorphism, cup-shaped ears and intellectual disability. Sanger sequencing of GORAB revealed the seemingly homozygous missense mutation p.Ser175Phe. This mutation was detected in a heterozygous state in the clinically unaffected mother, but was absent in the healthy father. We performed copy-number investigations by high-resolution array-CGH and PCR approaches and found an ~6 Mb de novo deletion spanning 1q23.3-q24.2 in the affected boy. This novel combination of genetic defects very well explains the phenotype that goes beyond the usual presentation of gerodermia osteodysplastica. Our data provide new insight into the phenotypic spectrum of 1q23-q25 deletions and shows that the combination with another pathogenic allele can lead to more severe clinical manifestations.

ALDH18A1-related cutis laxa syndrome with cyclic vomiting

Cutis laxa (CL) syndromes are connective tissue disorders characterized by redundant, sagging, inelastic and wrinkled skin, with organ involvement. Here, we describe a patient with ALDH18A1-related CL who developed cyclic vomiting. The patient was a 12-year-old boy who presented with poor postnatal growth, hypotonia, short stature, joint hyperlaxity, microcephaly, strabismus, bilateral cataracts, facial dysmorphism and severe mental retardation. Bone radiographs showed osteopenia and osteoporosis, and magnetic resonance angiography showed marked kinking and tortuosity of the brain vessels. These findings were clinically compatible with ALDH18A1-related CL. Molecular analysis revealed a de novo heterozygous mutation (p.R138Q) in ALDH18A1. No mutations were found in PYCR1 gene. The patient developed cyclic vomiting with decreased blood levels of ornithine, citrulline, arginine and proline without hyperammonemia and other hypoaminoacidemias were also found. ALDH18A1 encodes Δ(1)-pyrroline-5-carboxylate synthase, which is related to the biosynthesis of ornithine, citrulline, arginine, and proline. Cyclic vomiting has never been reported in other ALDH18A1-related CL patients. This is the first case report of ALDH18A1-related CL with cyclic vomiting associated with amino acid abnormalities.

Neurometabolic disorders: Five new things

Purpose of review

To present emerging issues in neurometabolic disorders, with an emphasis on the diagnostic workup of patients with suspected neurometabolic disorders and some future challenges in the care for these patients.

Recent findings

Next-generation sequencing and next-generation metabolic screening increase the speed and yield of the diagnostic process in neurometabolic disorders. Furthermore, they deepen our insights into the underlying disease mechanisms. Care of adult patients with neurometabolic disorders is an expanding subspecialty, especially in internal medicine and neurology.

Summary

We briefly discuss some novel genetic and biochemical laboratory techniques and changing insights in the molecular basis of disease, and illustrate the importance of MRI pattern recognition in the diagnostic process. Furthermore, we discuss gene therapy that is cautiously entering the field, and pay attention to the new field of (transition of) care for adult patients with inborn errors of metabolism.

PYCR2 Mutations cause a lethal syndrome of microcephaly and failure to thrive

OBJECTIVE

A study was undertaken to characterize the clinical features of the newly described hypomyelinating leukodystrophy type 10 with microcephaly. This is an autosomal recessive disorder mapped to chromosome 1q42.12 due to mutations in the PYCR2 gene, encoding an enzyme involved in proline synthesis in mitochondria.

METHODS

From several international clinics, 11 consanguineous families were identified with PYCR2 mutations by whole exome or targeted sequencing, with detailed clinical and radiological phenotyping. Selective mutations from patients were tested for effect on protein function.

RESULTS

The characteristic clinical presentation of patients with PYCR2 mutations included failure to thrive, microcephaly, craniofacial dysmorphism, progressive psychomotor disability, hyperkinetic movements, and axial hypotonia with variable appendicular spasticity. Patients did not survive beyond the first decade of life. Brain magnetic resonance imaging showed global brain atrophy and white matter T2 hyperintensities. Routine serum metabolic profiles were unremarkable. Both nonsense and missense mutations were identified, which impaired protein multimerization.

INTERPRETATION

PYCR2-related syndrome represents a clinically recognizable condition in which PYCR2 mutations lead to protein dysfunction, not detectable on routine biochemical assessments. Mutations predict a poor outcome, probably as a result of impaired mitochondrial function. Ann Neurol 2016;80:59-70.

Advantages and Pitfalls of Mass Spectrometry Based Metabolome Profiling in Systems Biology

Mass spectrometry-based metabolome profiling became the method of choice in systems biology approaches and aims to enhance biological understanding of complex biological systems. Genomics, transcriptomics, and proteomics are well established technologies and are commonly used by many scientists. In comparison, metabolomics is an emerging field and has not reached such high-throughput, routine and coverage than other omics technologies. Nevertheless, substantial improvements were achieved during the last years. Integrated data derived from multi-omics approaches will provide a deeper understanding of entire biological systems. Metabolome profiling is mainly hampered by its diversity, variation of metabolite concentration by several orders of magnitude and biological data interpretation. Thus, multiple approaches are required to cover most of the metabolites. No software tool is capable of comprehensively translating all the data into a biologically meaningful context yet. In this review, we discuss the advantages of metabolome profiling and main obstacles limiting progress in systems biology.