Zellweger syndrome and associated phenotypes

Prenatal Diagnosis by Trio Clinical Exome Sequencing: Single Center Experience

Fetal anomalies, characterized by structural or functional abnormalities occurring during intrauterine life, pose a significant medical challenge, with a notable prevalence, affecting approximately 2-3% of live births and 20% of spontaneous miscarriages. This study aims to identify the genetic cause of ultrasound anomalies through clinical exome sequencing (CES) analysis. The focus is on utilizing CES analysis in a trio setting, involving the fetuses and both parents. To achieve this objective, prenatal trio clinical exome sequencing was conducted in 51 fetuseses exhibiting ultrasound anomalies with previously negative results from chromosomal microarray (CMA) analysis. The study revealed pathogenic variants in 24% of the analyzed cases (12 out of 51). It is worth noting that the findings include de novo variants in 50% of cases and the transmission of causative variants from asymptomatic parents in 50% of cases. Trio clinical exome sequencing stands out as a crucial tool in advancing prenatal diagnostics, surpassing the effectiveness of relying solely on chromosomal microarray analysis. This underscores its potential to become a routine diagnostic standard in prenatal care, particularly for cases involving ultrasound anomalies.

Dynamic lipid turnover in photoreceptors and retinal pigment epithelium throughout life

The retinal pigment epithelium-photoreceptor interphase is renewed each day in a stunning display of cellular interdependence. While photoreceptors use photosensitive pigments to convert light into electrical signals, the RPE supports photoreceptors in their function by phagocytizing shed photoreceptor tips, regulating the blood retina barrier, and modulating inflammatory responses, as well as regenerating the 11-cis-retinal chromophore via the classical visual cycle. These processes involve multiple protein complexes, tightly regulated ligand-receptors interactions, and a plethora of lipids and protein-lipids interactions. The role of lipids in maintaining a healthy interplay between the RPE and photoreceptors has not been fully delineated. In recent years, novel technologies have resulted in major advancements in understanding several facets of this interplay, including the involvement of lipids in phagocytosis and phagolysosome function, nutrient recycling, and the metabolic dependence between the two cell types. In this review, we aim to integrate the complex role of lipids in photoreceptor and RPE function, emphasizing the dynamic exchange between the cells as well as discuss how these processes are affected in aging and retinal diseases.

Insufficiency of ciliary cholesterol in hereditary Zellweger syndrome

Primary cilia are antenna‐like organelles on the surface of most mammalian cells that receive sonic hedgehog (Shh) signaling in embryogenesis and carcinogenesis. Cellular cholesterol functions as a direct activator of a seven‐transmembrane oncoprotein called Smoothened (Smo) and thereby induces Smo accumulation on the ciliary membrane where it transduces the Shh signal. However, how cholesterol is supplied to the ciliary membrane remains unclear. Here, we report that peroxisomes are essential for the transport of cholesterol into the ciliary membrane. Zellweger syndrome (ZS) is a peroxisome‐deficient hereditary disorder with several ciliopathy‐related features and cells from these patients showed a reduced cholesterol level in the ciliary membrane. Reverse genetics approaches revealed that the GTP exchange factor Rabin8, the Rab GTPase Rab10, and the microtubule minus‐end‐directed kinesin KIFC3 form a peroxisome‐associated complex to control the movement of peroxisomes along microtubules, enabling communication between peroxisomes and ciliary pocket membranes. Our findings suggest that insufficient ciliary cholesterol levels may underlie ciliopathies.

Therapeutic microRNAs in polycystic kidney disease

PURPOSE OF REVIEW

microRNAs (miRNAs) are short noncoding RNAs that function as sequence-specific inhibitors of gene expression. Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent genetic cause of end-stage kidney failure with limited treatment options. The realization that miRNA upregulation, and thus its gain-of-function, can drive the progression of ADPKD has raised the possibility that anti-miRs represent a novel drug class for this disorder.

RECENT FINDINGS

A common set of miRNAs are aberrantly expressed in various murine models of polycystic kidney disease. In particular two miRNAs, miR-17 family and miR-21, are both upregulated in kidney cysts and promote ADPKD progression in mouse models. miR-17 rewires cyst epithelial metabolism to enhance cyst proliferation. On the other hand, miR-21 represses proapoptotic genes and thus inhibits cyst apoptosis. Importantly, an anti-miR-17 drug has advanced through preclinical ADPKD studies, whereas an anti-miR-21 drug has already cleared phase I clinical trial.

SUMMARY

miRNAs have emerged as new regulators of ADPKD pathogenesis. Anti-miRs represent a feasible and an entirely new class of drugs for the treatment of ADPKD.

microRNA-17 family promotes polycystic kidney disease progression through modulation of mitochondrial metabolism

Autosomal dominant polycystic kidney disease (ADPKD) is the most frequent genetic cause of renal failure. Here we identify miR-17 as a target for the treatment of ADPKD. We report that miR-17 is induced in kidney cysts of mouse and human ADPKD. Genetic deletion of the miR-17∼92 cluster inhibits cyst proliferation and PKD progression in four orthologous, including two long-lived, mouse models of ADPKD. Anti-miR-17 treatment attenuates cyst growth in short-term and long-term PKD mouse models. miR-17 inhibition also suppresses proliferation and cyst growth of primary ADPKD cysts cultures derived from multiple human donors. Mechanistically, c-Myc upregulates miR-17∼92 in cystic kidneys, which in turn aggravates cyst growth by inhibiting oxidative phosphorylation and stimulating proliferation through direct repression of Pparα. Thus, miR-17 family is a promising drug target for ADPKD, and miR-17-mediated inhibition of mitochondrial metabolism represents a potential new mechanism for ADPKD progression.

Autosomal dominant polycystic kidney disease (ADPKD) is a life-threatening genetic disease that leads to renal failure. Here Hajarnis et al. show that miR-17 modulates cyst progression in ADPKD through metabolic reprogramming of mitochondria and its inhibition slows cyst development and improves renal functions.

The placenta findings from an XYY abortus: a case report

INTRODUCTION

The placenta morphology from an XYY pregnancy abortus has not been reported in the medical literature. This case report consists of the first detailed documentation. The reported case is also highly unusual because the mother had two prior pregnancies with fetuses being confirmed to have Zellweger syndrome and one prior molar pregnancy.

CASE PRESENTATION

A 43-year-old Caucasian woman presented for induction of labor secondary to diagnosis of XYY chromosomes by chorionic villus sample.

CONCLUSIONS

This is the first detailed observation of placenta morphology in an XYY abortus. Although not highly specific, the observation is very unique and should prompt further investigation of karyotyping of the fetus or infant because an XYY individual may be viable and grow to adulthood. The association of an XYY abortus and prior pregnancies with Zellweger syndrome and one prior molar pregnancy is also highly notable.

Zellweger syndrome and associated brain malformations: report of a novel Peroxin1 (PEX1) mutation in a Native American infant

Zellweger syndrome (cerebrohepatorenal syndrome) is very rare and is the most severe form of peroxisomal biogenesis disorders. These can be caused by mutations in any of the currently known Peroxin genes and typically present in the neonatal period with multiorgan involvement. Patients usually do not survive beyond 1 year of age. This article reports a case of Zellweger syndrome in a male Native American infant confirmed by clinical findings, imaging studies, and biochemical analysis. Genetic studies show a novel mutation (c.3030G>T, p. Glutamine1010Histidine) altering the last nucleotide of exon 19 in the Peroxin1 (PEX1) gene.

Zellweger syndrome: A cause of neonatal hypotonia and seizures

Zellweger syndrome, a paradigm of human peroxisomal disorders is characterized by dysmorphic features, hypotonia, severe neuro-developmental delay, hepatomegaly, renal cysts, sensorineural deafness and retinal dysfunction. This is a case report of a baby boy born with facial dysmorphism, profound hypotonia, seizures, and hepatomegaly. The diagnosis was not evident initially but only later when he presented with obstructive jaundiced and renal cysts. He died at the age of seven months. Biochemical studies revealed elevation of very long chain fatty acids and phytanic acid consistent with a peroxisomal disorder. The recognition of this syndrome is important since it is a fatal hereditary disease. Zellweger syndrome should be included in the differential diagnosis of infantile hypotonia and dysmorphism.

Oral cholic acid for hereditary defects of primary bile acid synthesis: a safe and effective long-term therapy

BACKGROUND & AIMS

Oral bile acid replacement has been shown to be an effective therapy in primary bile acid synthesis defects, but to date there have been no reports of the long-term effects of this therapy. The aim of the study was to evaluate the long-term effectiveness and safety of cholic acid (CA) therapy.

METHODS

Fifteen patients with either 3beta-hydroxy-Delta(5)-C(27)-steroid oxidoreductase (3beta-HSD) (n = 13) or Delta(4)-3-oxosteroid 5beta-reductase (Delta(4)-3-oxo-R) (n = 2) deficiency confirmed by mass spectrometry and gene sequencing received oral CA and were followed up prospectively.

RESULTS

CA therapy was started at a median age of 3.9 years (range, 0.3-13.1 years). The median follow-up with treatment was 12.4 years (range, 5.6-15 years). The mean daily dose of CA was initially 13 mg/kg and was 6 mg/kg at last evaluation. During CA therapy, physical examination findings, laboratory test results, and findings on sonography normalized. Mass spectrometry analysis of urine showed that excretion of the atypical metabolites was reduced by 500-fold and 30-fold in 3beta-HSD and Delta(4)-3-oxo-R deficiency, respectively, and total urinary bile acid excretion decreased dramatically. Liver biopsies performed in 14 patients after at least 5 years of CA therapy showed marked improvement, especially in patients with the 3beta-HSD deficiency. CA was well tolerated with all children developing normally, including 2 women having 4 normal pregnancies during treatment.

CONCLUSIONS

Oral CA therapy is a safe and effective long-term treatment of the most common primary bile acid synthesis defects.

PEX1mutations in the Zellweger spectrum of the peroxisome biogenesis disorders

Diseases of the Zellweger spectrum represent a major subgroup of the peroxisome biogenesis disorders, a group of autosomal-recessive diseases that are characterized by widespread tissue pathology, including neurodegeneration. The Zellweger spectrum represents a clinical continuum, with Zellweger syndrome (ZS) having the most severe phenotype, and neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD) having progressively milder phenotypes. Mutations in the PEX1 gene, which encodes a 143-kDa AAA ATPase protein required for peroxisome biogenesis, are the most common cause of the Zellweger spectrum diseases. The PEX1 mutations identified to date comprise insertions, deletions, nonsense, missense, and splice site mutations. Mutations that produce premature truncation codons (PTCs) are distributed throughout the PEX1 gene, whereas the majority of missense mutations segregate with the two essential AAA domains of the PEX1 protein. Severity at the two ends of the Zellweger spectrum correlates broadly with mutation type and impact (i.e., the severe ZS correlates with PTCs on both alleles, and the milder phenotypes correlate with missense mutations), but exceptions to these general correlations exist. This article provides an overview of the currently known PEX1 mutations, and includes, when necessary, revised mutation nomenclature and genotype-phenotype correlations that may be useful for clinical diagnosis.

Comparative physical and transcript maps of approximately 1 Mb around loop-tail, a gene for severe neural tube defects on distal mouse chromosome 1 and human chromosome 1q22-q23

The homozygous loop-tail (Lp) mouse has a severe neural tube closure defect, analogous to the craniorachischisis phenotype seen in humans. Linkage analysis and physical mapping have previously localized the Lp locus to a region on mouse chromosome 1 defined by the markers D1Mit113-Tagln2. Here we report the construction of sequence-ready bacterial clone contigs encompassing the Lp critical region in both mouse and the orthologous human region (1q22-q23). Twenty-two genes, one EST, and one pseudogene have been identified using a combination of EST database screening, exon amplification, and genomic sequence analysis. The preliminary gene map is Cen-Estm33-AA693056-Ly9-Cd48-Slam-Cd84-Kiaa1215-Nhlh1-Kiaa0253-Copa-Pxf-H326-Pea15-Casq1-Atp1a4-Atp1a2-Estm34-Kcnj9-Kcnj10-Kiaa1355-Tagln2-Nesg1-Crp-Tel. The genes between Slam and Kiaa1355 are positional candidates for Lp. The comparative gene content and order are identical between mouse and human, indicating a high degree of conservation between the two species in this region. Together, the physical and transcript maps described here serve as resources for the identification of the Lp mutation and further define the conservation of this genomic region between mouse and human.