Hepatocyte-specific deletion of peroxisomal protein PEX13 results in disrupted iron homeostasis.

Peroxisomes are organelles, abundant in the liver, involved in a variety of cellular functions, including fatty acid metabolism, plasmalogen synthesis and metabolism of reactive oxygen species. Several inherited disorders are associated with peroxisomal dysfunction; increasingly many are associated with hepatic pathologies. The liver plays a principal role in regulation of iron metabolism.

Impaired neurogenesis and associated gliosis in mouse brain with PEX13 deficiency.

Zellweger syndrome (ZS), a neonatal lethal disorder arising from defective peroxisome biogenesis, features profound neuroanatomical abnormalities and brain dysfunction. Here we used mice with brain-restricted inactivation of the peroxisome biogenesis gene PEX13 to model the pathophysiological features of ZS, and determine the impact of peroxisome dysfunction on neurogenesis and cell maturation in ZS. In the embryonic and postnatal PEX13 mutant brain, we demonstrate key regions with altered brain anatomy, including enlarged lateral ventricles and aberrant cortical, hippocampal and hypothalamic organization.

Peroxisomal protein PEX13 functions in selective autophagy.

PEX13 is an integral membrane protein on the peroxisome that regulates peroxisomal matrix protein import during peroxisome biogenesis. Mutations in PEX13 and other peroxin proteins are associated with Zellweger syndrome spectrum (ZSS) disorders, a subtype of peroxisome biogenesis disorder characterized by prominent neurological, hepatic, and renal abnormalities leading to neonatal death. The lack of functional peroxisomes in ZSS patients is widely accepted as the underlying cause of disease; however, our understanding of disease pathogenesis is still incomplete.

Mitochondrial changes and oxidative stress in a mouse model of Zellweger syndrome neuropathogenesis.

Zellweger syndrome (ZS) is a peroxisome biogenesis disorder that involves significant neuropathology, the molecular basis of which is still poorly understood. Using a mouse model of ZS with brain-restricted deficiency of the peroxisome biogenesis protein PEX13, we demonstrated an expanded and morphologically modified brain mitochondrial population. Cultured fibroblasts from PEX13-deficient mouse embryo displayed similar changes, as well as increased levels of mitochondrial superoxide and membrane depolarization; this phenotype was rescued by antioxidant treatment.

Mechanism of impaired microtubule-dependent peroxisome trafficking and oxidative stress in SPAST-mutated cells from patients with Hereditary Spastic Paraplegia.

Hereditary spastic paraplegia (HSP) is an inherited neurological condition that leads to progressive spasticity and gait abnormalities. Adult-onset HSP is most commonly caused by mutations in SPAST, which encodes spastin a microtubule severing protein. In olfactory stem cell lines derived from patients carrying different SPAST mutations, we investigated microtubule-dependent peroxisome movement with time-lapse imaging and automated image analysis.

A new disaster victim identification management strategy targeting "near identification-threshold" cases: Experiences from the Boxing Day tsunami.

The international disaster victim identification (DVI) response to the Boxing Day tsunami, led by the Royal Thai Police in Phuket, Thailand, was one of the largest and most complex in DVI history. Referred to as the Thai Tsunami Victim Identification operation, the group comprised a multi-national, multi-agency, and multi-disciplinary team. The traditional DVI approach proved successful in identifying a large number of victims quickly.

Low dose tubulin-binding drugs rescue peroxisome trafficking deficit in patient-derived stem cells in Hereditary Spastic Paraplegia.

Hereditary Spastic Paraplegia (HSP) is a genetically heterogeneous group of disorders, diagnosed by progressive gait disturbances with muscle weakness and spasticity, for which there are no treatments targeted at the underlying pathophysiology. Mutations in spastin are a common cause of HSP. Spastin is a microtubule-severing protein whose mutation in mouse causes defective axonal transport.

Revisiting the neuropathogenesis of Zellweger syndrome.

Zellweger syndrome (ZS) is a neonatal-lethal genetic disease that affects all tissues, and features neuropathology that involves primary developmental defects as well as neurodegeneration. Neuropathological changes include abnormal neuronal migration affecting the cerebral hemispheres, cerebellum and inferior olivary complex, abnormal Purkinje cell arborisation, demyelination and post-developmental neuronal degeneration. ZS is caused by mutations in peroxisome biogenesis, or PEX, genes which lead to defective peroxisome biogenesis and the resultant loss of peroxisomal metabolic function.

Excess iron modulates endoplasmic reticulum stress-associated pathways in a mouse model of alcohol and high-fat diet-induced liver injury.

Endoplasmic reticulum (ER) stress is an important pathogenic mechanism for alcoholic (ALD) and nonalcoholic fatty liver disease (NAFLD). Iron overload is an important cofactor for liver injury in ALD and NAFLD, but its role in ER stress and associated stress signaling pathways is unclear. To investigate this, we developed a murine model of combined liver injury by co-feeding the mildly iron overloaded, the hemochromatosis gene-null (Hfe(-/)) mouse ad libitum with ethanol and a high-fat diet (HFD) for 8 weeks.

The biogenesis protein PEX14 is an optimal marker for the identification and localization of peroxisomes in different cell types, tissues, and species in morphological studies.

Catalase and ABCD3 are frequently used as markers for the localization of peroxisomes in morphological experiments. Their abundance, however, is highly dependent on metabolic demands, reducing the validity of analyses of peroxisomal abundance and distribution based solely on these proteins. We therefore attempted to find a protein which can be used as an optimal marker for peroxisomes in a variety of species, tissues, cell types and also experimental designs, independently of peroxisomal metabolism.

RhoA regulation of cardiomyocyte differentiation.

Earlier findings from our laboratory implicated RhoA in heart developmental processes. To investigate factors that potentially regulate RhoA expression, RhoA gene organisation and promoter activity were analysed. Comparative analysis indicated strict conservation of both gene organisation and coding sequence of the chick, mouse, and human RhoA genes.

Glucocorticoids alleviate intestinal ER stress by enhancing protein folding and degradation of misfolded proteins.

Endoplasmic reticulum (ER) stress in intestinal secretory cells has been linked with colitis in mice and inflammatory bowel disease (IBD). Endogenous intestinal glucocorticoids are important for homeostasis and glucocorticoid drugs are efficacious in IBD. In Winnie mice with intestinal ER stress caused by misfolding of the Muc2 mucin, the glucocorticoid dexamethasone (DEX) suppressed ER stress and activation of the unfolded protein response (UPR), substantially restoring goblet cell Muc2 production.

PEX13 deficiency in mouse brain as a model of Zellweger syndrome: abnormal cerebellum formation, reactive gliosis and oxidative stress.

Delayed cerebellar development is a hallmark of Zellweger syndrome (ZS), a severe neonatal neurodegenerative disorder. ZS is caused by mutations in PEX genes, such as PEX13, which encodes a protein required for import of proteins into the peroxisome. The molecular basis of ZS pathogenesis is not known.

alpha-Synuclein abnormalities in mouse models of peroxisome biogenesis disorders.

alpha-Synuclein (alphaS) is a presynaptic protein implicated in Parkinson's disease (PD). Growing evidence implicates mitochondrial dysfunction, oxidative stress, and alphaS-lipid interactions in the gradual accumulation of alphaS in pathogenic forms and its deposition in Lewy bodies, the pathological hallmark of PD and related synucleinopathies. The peroxisomal biogenesis disorders (PBD), with Zellweger syndrome serving as the prototype of this group, are characterized by malformed and functionally impaired peroxisomes.

Quantitative genotyping of mouse brain-specific PEX13 gene disruption by real-time PCR.

The Cre/loxP-system has become an invaluable tool for the generation of tissue-specific gene disruption in mice. However, because Cre recombinase excision of individual genes can be variable, an accurate and sensitive method is necessary to determine the ultimate level of gene disruption. The analysis of gene disruption is particularly difficult for tissue that has been fixed for (immuno)histochemical analysis with paraformaldehyde.

Fuzzy scaling analysis of a mouse mutant with brain morphological changes.

Scaling behavior inherently exists in fundamental biological structures, and the measure of such an attribute can only be known at a given scale of observation. Thus, the properties of fractals and power-law scaling have become attractive for research in biology and medicine because of their potential for discovering patterns and characteristics of complex biological morphologies. Despite the successful applications of fractals for the life sciences, the quantitative measure of the scale invariance expressed by fractal dimensions is limited in more complex situations, such as for histopathological analysis of tissue changes in disease.

A region analysis approach for segmenting neural-cell images.

In this paper we present new algorithms based on region analysis of grey and distance differences of images that successfully circumvent these problems. Two key parameters of this analysis, window width and logical threshold, are automatically extracted for use in logical thresholding, and spurious regions are detected and removed through use of a hierarchical window filter. The efficacy of the developed algorithms is demonstrated here through an analysis of cultured brain neurons from newborn mice.

Segmentation of cultured neurons using logical analysis of grey and distance difference.

The molecular and cellular bases of neuronal cell death that underpin a wide range of neurodegenerative disorders are still not well understood. One approach to investigating neuronal death is through systematic studies of the changing morphology of cultured brain neurons in response to cellular challenges. Image segmentation methods developed to date to analyze such changes have been limited by the low contrast of cells in unstained neuronal cultures and the unimodal histograms generated by these analyses.

Segmentation of neuronal-cell images from stained fields and monomodal histograms.

Information from images taken of cells being grown in culture with oxidative agents allows life science researchers to compare changes in neurons from the Zellweger mice to those from normal mice. Image segmentation is the major and first step for the study of these different types of processes in cells. In this paper we develop an innovative strategy for the segmentation of neuronal-cell images which are subjected to stains and whose histograms are monomodal.

Failure of microtubule-mediated peroxisome division and trafficking in disorders with reduced peroxisome abundance.

In contrast to peroxisomes in normal cells, remnant peroxisomes in cultured skin fibroblasts from a subset of the clinically severe peroxisomal disorders that includes the biogenesis disorder Zellweger syndrome and the single-enzyme defect D-bifunctional protein (D-BP) deficiency, are enlarged and significantly less abundant. We tested whether these features could be related to the known role of microtubules in peroxisome trafficking in mammalian cells. We found that remnant peroxisomes in fibroblasts from patients with PEX1-null Zellweger syndrome or D-BP deficiency exhibited clustering and loss of alignment along peripheral microtubules.

Novel PEX1 coding mutations and 5' UTR regulatory polymorphisms.

Zellweger syndrome and its milder variants--neonatal adrenoleukodystrophy and infantile Refsum disease--comprise a clinical continuum of diseases referred to as the Zellweger spectrum. Mutations in the PEX1 gene, which consists of 24 exons and encodes a AAA ATPase protein required for peroxisomal protein import, account for approximately two-thirds of the known Zellweger spectrum patient mutations. In this paper, we report on four novel PEX1 mutations and two polymorphisms in an Australasian cohort.

PEX1 mutations 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.

Extraction of fluorescent cell puncta by adaptive fuzzy segmentation.

Motivation: The discrimination and measurement of fluorescent-labeled vesicles using microscopic analysis of fixed cells presents a challenge for biologists interested in quantifying the abundance, size and distribution of such vesicles in normal and abnormal cellular situations. In the specific application reported here, we were interested in quantifying changes to the population of a major organelle, the peroxisome, in cells from normal control patients and from patients with a defect in peroxisome biogenesis. In the latter, peroxisomes are present as larger vesicular structures with a more restricted cytoplasmic distribution.

Pex13 inactivation in the mouse disrupts peroxisome biogenesis and leads to a Zellweger syndrome phenotype.

Zellweger syndrome is the archetypical peroxisome biogenesis disorder and is characterized by defective import of proteins into the peroxisome, leading to peroxisomal metabolic dysfunction and widespread tissue pathology. In humans, mutations in the PEX13 gene, which encodes a peroxisomal membrane protein necessary for peroxisomal protein import, can lead to a Zellweger phenotype. To develop mouse models for this disorder, we have generated a targeted mouse with a loxP-modified Pex13 gene to enable conditional Cre recombinase-mediated inactivation of Pex13.

RhoA is highly up-regulated in the process of early heart development of the chick and important for normal embryogenesis.

We have used molecular techniques, combined with classic embryological methods, to identify up-regulated genes associated with early heart development. One of the cDNAs identified and isolated by screening a chick lambda cDNA library was the small guanosine triphosphatase RhoA. RhoA has at least three different length mRNA species, each varying in the length of the 3' untranslated region.