Adenylosuccinate lyase deficiency: the first identified polish patient

Effect of toyF on wuyiencin and toyocamycin production by Streptomyces albulus CK-15

Streptomyces albulus CK-15 produces various secondary metabolites, including the antibiotics wuyiencin and toyocamycin, which can reportedly control a broad range of plant fungal diseases. The production of these nucleoside antibiotics in CK-15 is regulated by two biosynthesis gene clusters. To investigate the potential effect of toyocamycin biosynthesis on wuyiencin production, we herein generated S. albulus strains in which a key gene in the toyocamycin biosynthesis gene cluster, namely toyF, was either deleted or overexpressed. The toyF deletion mutant ∆toyF did not produce toyocamycin, while the production of wuyiencin increased by 23.06% in comparison with that in the wild-type (WT) strain. In addition, ΔtoyF reached the highest production level of wuyiencin 4 h faster than the WT strain (60 h vs. and 64 h). Further, toyocamycin production by the toyF overexpression strain was two-fold higher than by the WT strain, while wuyiencin production was reduced by 29.10%. qRT-PCR showed that most genes in the toyocamycin biosynthesis gene cluster were expressed at lower levels in ∆toyF as compared with those in the WT strain, while the expression levels of genes in the wuyiencin biosynthesis gene cluster were upregulated. Finally, the growth rate of ∆toyF was much faster than that of the WT strain when cultured on solid or liquid medium. Based on our findings, we report that in industrial fermentation processes, ∆toyF has the potential to increase the production of wuyiencin and reduce the timeframe of fermentation.

Clinical and molecular characterization of patients with adenylosuccinate lyase deficiency

Background

Adenylosuccinate lyase deficiency (ADSLD) is an ultrarare neurometabolic recessive disorder caused by loss-of-function mutations in the ADSL gene. The disease is characterized by wide clinical variability. Here we provide an updated clinical profiling of the disorder and discuss genotype–phenotype correlations.

Results

Data were collected through "Our Journey with ADSL deficiency Association" by using a dedicated web survey filled-in by parents.

Clinical and molecular data were collected from 18 patients (12 males, median age 10.9 years ± 7.3), from 13 unrelated families. The age at onset ranged from birth to the first three years (median age 0.63 years ± 0.84 SD), and age at diagnosis varied from 2 months to 17 years, (median age 6.4 years ± 6.1 SD). The first sign was a psychomotor delay in 8/18 patients, epilepsy in 3/18, psychomotor delay and epilepsy in 3/18, and apneas, hypotonia, nystagmus in single cases. One patient (sibling of a previously diagnosed child) had a presymptomatic diagnosis. The diagnosis was made by exome sequencing in 7/18 patients. All patients were definitively diagnosed with ADSL deficiency based on pathogenic variants and/or biochemical assessment. One patient had a fatal neonatal form of ADSL deficiency, seven showed features fitting type I, and nine were characterized by a milder condition (type II), with two showing a very mild phenotype. Eighteen different variants were distributed along the entire ADSL coding sequence and were predicted to have a variable structural impact by impairing proper homotetramerization or catalytic activity of the enzyme. Six variants had not previously been reported. All but two variants were missense.

Conclusions

The study adds more details on the spectrum of ADSLD patients’ phenotypes and molecular data.

Adenylosuccinate lyase deficiency

Adenylosuccinate lyase ADSL) deficiency is a defect of purine metabolism affecting purinosome assembly and reducing metabolite fluxes through purine de novo synthesis and purine nucleotide recycling pathways. Biochemically this defect manifests by the presence in the biologic fluids of two dephosphorylated substrates of ADSL enzyme: succinylaminoimidazole carboxamide riboside (SAICAr) and succinyladenosine (S-Ado). More than 80 individuals with ADSL deficiency have been identified, but incidence of the disease remains unknown. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The fatal neonatal form has onset from birth and presents with fatal neonatal encephalopathy with a lack of spontaneous movement, respiratory failure, and intractable seizures resulting in early death within the first weeks of life. Patients with type I (severe form) present with a purely neurologic clinical picture characterized by severe psychomotor retardation, microcephaly, early onset of seizures, and autistic features. A more slowly progressing form has also been described (type II, moderate or mild form), as having later onset, usually within the first years of life, slight to moderate psychomotor retardation and transient contact disturbances. Diagnosis is facilitated by demonstration of SAICAr and S-Ado in extracellular fluids such as plasma, cerebrospinal fluid and/or followed by genomic and/or cDNA sequencing and characterization of mutant proteins. Over 50 ADSL mutations have been identified and their effects on protein biogenesis, structural stability and activity as well as on purinosome assembly were characterized. To date there is no specific and effective therapy for ADSL deficiency.

Magnetic resonance imaging of the brain in adenylosuccinate lyase deficiency: a report of seven cases and a review of the literature

Adenylosuccinate lyase (ADSL) deficiency is a rare autosomal recessive disorder of purine metabolism. Patients may present with a wide range of neurological symptoms. Head imaging abnormalities have been reported only rarely in the scientific literature and include atrophy of the cerebral cortex, corpus callosum, cerebellar vermis, lack of myelination, delayed myelination, anomalies of the white matter, and lissencephaly. The pathogenesis of abnormalities remains unknown. To further the understanding of the spectrum of brain abnormalities associated with ADSL deficiency, we examined the magnetic resonance findings in seven Polish patients with different clinical phenotypes and genotypes. Head MRI showed impaired white matter myelination with various degrees of global supra- and infratentorial white matter loss including widening of the lateral ventricles, enlargement of the subarachnoid spaces, atrophy of the cerebrum, hypoplasia of the cerebellar hemispheres and enlargement of the cisterna magna, and white matter abnormal hyperintense signal on T(2)-weighted sequences. We recommend performing a detailed analysis of urine and plasma purine metabolites in patients who have neurological findings, including developmental delay, microcephaly, autistic features, neonatal encephalopathy, and seizures especially if MRI findings such as delayed or lack of myelination, white matter abnormal signal, and atrophy of the cerebrum and/or cerebellum are also present. Greater awareness of adenylosuccinate lyase deficiency among general pediatricians, neonatologists, pediatric neurologists, and also radiologists is the key to identifying the disorder at an early stage.

Clinical, biochemical and molecular findings in seven Polish patients with adenylosuccinate lyase deficiency

Adenylosuccinate lyase (ADSL) catalyzes two steps in purine nucleotide metabolism-the 8th step in the de novo pathway: conversion of succinylaminoimidazole carboxamide ribotide (SAICAR) to aminoimidazole carboxamide ribotide (AICAR), and conversion of adenylosuccinate (S-AMP) to adenylate (AMP) in the purine nucleotide cycle. To date, over 50 patients have been reported suffering from ADSL deficiency. We report all seven so far diagnosed Polish patients with this defect. Most of our patients shared intractable seizures and psychomotor retardation since the neonatal period and had biochemical evidence of severe (type I) deficiency. Two patients with type II suffered only from mild/moderate psychomotor retardation and showed a transientvisual contact disturbance. One patient had a fatal neonatal form of ADSL deficiency with lack of spontaneous movement, respiratory failure, severe encephalopathy and intractable seizures. Analysis of the ADSL gene showed that four apparently unrelated patients carried a R426H mutation (two homozygous and two compound heterozygous). With the exception of the latter mutation, a Y114H mutation that had been reported previously, and a novel mutation T242I, all other mutations (including D268H and three novel S23R, D215H and I351T mutations) were found only in single families in single alleles. A search for this disorder should be included in the screening program of all infants with unexplained neonatal seizures, severe infantile epileptic encephalopathy, developmental delay, hypotonia, and/or autistic features.