Deficiency of ferritin heavy-chain nuclear import in triple a syndrome implies nuclear oxidative damage as the primary disease mechanism

Generation of glucocorticoid-producing cells derived from human pluripotent stem cells

Adrenal insufficiency is a life-threatening condition resulting from the inability to produce adrenal hormones in a dose- and time-dependent manner. Establishing a cell-based therapy would provide a physiologically responsive approach for the treatment of this condition. We report the generation of large numbers of human-induced steroidogenic cells (hiSCs) from human pluripotent stem cells (hPSCs). Directed differentiation of hPSCs into hiSCs recapitulates the initial stages of human adrenal development. Following expression of steroidogenic factor 1, activation of protein kinase A signaling drives a steroidogenic gene expression profile most comparable to human fetal adrenal cells, and leads to dynamic secretion of steroid hormones, in vitro. Moreover, expression of the adrenocorticotrophic hormone (ACTH) receptor/co-receptor (MC2R/MRAP) results in dose-dependent ACTH responsiveness. This protocol recapitulates adrenal insufficiency resulting from loss-of-function mutations in AAAS, which cause the enigmatic triple A syndrome. Our differentiation protocol generates sufficient numbers of hiSCs for cell-based therapy and offers a platform to study disorders causing adrenal insufficiency.

The Oxidative Stress and Nervous Distress Connection in Gastrointestinal Disorders

Oxidative stress is increasingly recognized as a central player in a range of gastrointestinal (GI) disorders, as well as complications stemming from therapeutic interventions. This article presents an overview of the mechanisms of oxidative stress in GI conditions and highlights a link between oxidative insult and disruption to the enteric nervous system (ENS), which controls GI functions. The dysfunction of the ENS is characteristic of a spectrum of disorders, including neurointestinal diseases and conditions such as inflammatory bowel disease (IBD), diabetic gastroparesis, and chemotherapy-induced GI side effects. Neurons in the ENS, while essential for normal gut function, appear particularly vulnerable to oxidative damage. Mechanistically, oxidative stress in enteric neurons can result from intrinsic nitrosative injury, mitochondrial dysfunction, or inflammation-related pathways. Although antioxidant-based therapies have shown limited efficacy, recognizing the multifaceted role of oxidative stress in GI diseases offers a promising avenue for future interventions. This comprehensive review summarizes the literature to date implicating oxidative stress as a critical player in the pathophysiology of GI disorders, with a focus on its role in ENS injury and dysfunction, and highlights opportunities for the development of targeted therapeutics for these diseases.

SCARB1 downregulation in adrenal insufficiency with Allgrove syndrome

BACKGROUND

Allgrove disease is a rare genetic syndrome characterized by adrenal insufficiency, alacrimia, achalasia and complex neurological involvement. Allgrove disease is due to recessive mutations in the AAAS gene, which encodes for the nucleoporin Aladin, implicated in the nucleocytoplasmic transport. The adrenal insufficiency has been suggested to rely on adrenal gland-ACTH resistance. However, the link between the molecular pathology affecting the nucleoporin Aladin and the glucocorticoid deficiency is still unknown.

RESULTS

By analyzing postmortem patient's adrenal gland, we identified a downregulation of Aladin transcript and protein. We found a downregulation of Scavenger receptor class B-1 (SCARB1), a key component of the steroidogenic pathway, and SCARB1 regulatory miRNAs (mir125a, mir455) in patient's tissues. With the hypothesis of an impairment in the nucleocytoplasmic transport of the SCARB1 transcription enhancer cyclic AMP-dependent protein kinase (PKA), we detected a reduction of nuclear Phospho-PKA and a cytoplasmic mislocalization in patient's samples.

CONCLUSIONS

These results shed a light on the possible mechanisms linking ACTH resistance, SCARB1 impairment, and defective nucleocytoplasmic transport.

Rare forms of genetic paediatric adrenal insufficiency: Excluding congenital adrenal hyperplasia

Adrenal insufficiency (AI) is a severe endocrine disorder characterized by insufficient glucocorticoid (GC) and/or mineralocorticoid (MC) secretion by the adrenal glands, due to impaired adrenal function (primary adrenal insufficiency, PAI) or to insufficient adrenal stimulation by pituitary ACTH (secondary adrenal insufficiency, SAI) or tertiary adrenal insufficiency due to hypothalamic dysfunction. In this review, we describe rare genetic causes of PAI with isolated GC or combined GC and MC deficiencies and we also describe rare syndromes of isolated MC deficiency. In children, the most frequent cause of PAI is congenital adrenal hyperplasia (CAH), a group of adrenal disorders related to steroidogenic enzyme deficiencies, which will not be included in this review. Less frequently, several rare diseases can cause PAI, either affecting exclusively the adrenal glands or with systemic involvement. The diagnosis of these diseases is often challenging, due to the heterogeneity of their clinical presentation and to their rarity. Therefore, the current review aims to provide an overview on these rare genetic forms of paediatric PAI, offering a review of genetic and clinical features and a summary of diagnostic and therapeutic approaches, promoting awareness among practitioners, and favoring early diagnosis and optimal clinical management in suspect cases.

The clinical and laboratory features of patients with triple A syndrome: a single-center experience in Turkey

AIM

Triple-A Syndrome (TAS) is a rare autosomal recessive disorder characterized by adrenal insufficiency, achalasia, and alacrimia. This disorder is caused by mutations in the AAAS gene. The aim of this study is to discuss the clinical, laboratory and molecular genetic analysis results of 12 patients with TAS.

METHOD

We evaluated 12 patients from 8 families. Clinical and laboratory data were retrospectively collected from the medical records of the patients in the database for the period 2015-2020. All exons and exon-intron junctions of the AAAS gene were evaluated by next-generation sequencing method. Detected variants were classified according to American Collage of Medical Genetics criteria.

RESULTS

Alacrimia was found in all patients (100%); achalasia was found in 10 patients (83.3%) and adrenal insufficiency was found in 10 patients (83.3%). In addition, hyperreflexia(6/12), learning disability(5/12), hypernasal speech(5/12), muscle weakness(8/12), delayed walking(7/12), delayed speech(6/12), excessive sweating(7/12), optic atrophy(1/12), epilepsy(1/12), palmoplantar hyperkeratosis(5/12), multiple dental caries(9/12), atrophy of the thenar/hypothenar muscles(4/12) and short stature(4/12) were detected. The DHEA-S levels were measured in 10 patients and were found to be low in 8 of them. In all patients, the sodium and potassium levels were found to be normal. AAAS gene sequencing revealed four previously reported c.1066_1067del (p.Leu356fs*8), c.1432 C > T (p.Arg478*), c.688 C > T (p.Arg230*), and c.1368_1372del (p.Gln456fs*38) variants and two novel homozygous c.1250-1 G > A and c.398_399 + 2del variants in the AAAS gene.

CONCLUSION

We detected two novel variants in the AAAS gene. While the classic triad is present in 66.7% of the cases, neurological dysfunction, skin and dental pathologies also occur quite frequently. The earliest and most common finding of TAS is alacrimia. Therefore, adrenal insufficiency should be investigated in all patients with alacrimia and if necessary, genetic analysis should be performed for TAS. In addition, TAS should be followed up with a multidisciplinary approach since it involves many systems.

History of Adrenal Research: From Ancient Anatomy to Contemporary Molecular Biology

The adrenal is a small, anatomically unimposing structure that escaped scientific notice until 1564 and whose existence was doubted by many until the 18th century. Adrenal functions were inferred from the adrenal insufficiency syndrome described by Addison and from the obesity and virilization that accompanied many adrenal malignancies, but early physiologists sometimes confused the roles of the cortex and medulla. Medullary epinephrine was the first hormone to be isolated (in 1901), and numerous cortical steroids were isolated between 1930 and 1949. The treatment of arthritis, Addison's disease, and congenital adrenal hyperplasia (CAH) with cortisone in the 1950s revolutionized clinical endocrinology and steroid research. Cases of CAH had been reported in the 19th century, but a defect in 21-hydroxylation in CAH was not identified until 1957. Other forms of CAH, including deficiencies of 3β-hydroxysteroid dehydrogenase, 11β-hydroxylase, and 17α-hydroxylase were defined hormonally in the 1960s. Cytochrome P450 enzymes were described in 1962-1964, and steroid 21-hydroxylation was the first biosynthetic activity associated with a P450. Understanding of the genetic and biochemical bases of these disorders advanced rapidly from 1984 to 2004. The cloning of genes for steroidogenic enzymes and related factors revealed many mutations causing known diseases and facilitated the discovery of new disorders. Genetics and cell biology have replaced steroid chemistry as the key disciplines for understanding and teaching steroidogenesis and its disorders.

Ferritin Heavy Chain Binds Peroxiredoxin 6 and Inhibits Cell Proliferation and Migration

The H Ferritin subunit (FTH1), as well as regulating the homeostasis of intracellular iron, is involved in complex pathways that might promote or inhibit carcinogenesis. This function may be mediated by its ability to interact with different molecules. To gain insight into the FTH1 interacting molecules, we analyzed its interactome in HEK293T cells. Fifty-one proteins have been identified, and among them, we focused our attention on a member of the peroxiredoxin family (PRDX6), an antioxidant enzyme that plays an important role in cell proliferation and in malignancy development. The FTH1/PRDX6 interaction was further supported by co-immunoprecipitation, in HEK293T and H460 cell lines and by means of computational methods. Next, we demonstrated that FTH1 could inhibit PRDX6-mediated proliferation and migration. Then, the results so far obtained suggested that the interaction between FTH1/PRDX6 in cancer cells might alter cell proliferation and migration, leading to a less invasive phenotype.

Nuclear Pore Dysfunction in Neurodegeneration

The nuclear pore complex (NPC) is a large multimeric structure that is interspersed throughout the membrane of the nucleus and consists of at least 33 protein components. Individual components cooperate within the nuclear pore to facilitate selective passage of materials between the nucleus and cytoplasm while simultaneously performing pore-independent roles throughout the cell. NPC dysfunction is a hallmark of neurodegenerative disorders including Alzheimer's disease, Huntington's disease, and amyotrophic lateral sclerosis (ALS). NPC components can become mislocalized or altered in expression in neurodegeneration. These alterations in NPC structure are often detrimental to the neuronal function and ultimately lead to neuronal loss. This review highlights the importance of nucleocytoplasmic transport and NPC integrity and how dysfunction of such may contribute to neurodegeneration.

Proteomic changes in broiler liver by body weight differences under chronic heat stress

The increasing global temperature is causing economic losses and animal welfare problems in the poultry industry. Because poultry do not have sweat glands, it is difficult for them to return to their usual body temperature. Heat stress has negative impact on production and health in broilers. Given the effects of chronic stress on broilers, the objective of this study was to identify physiological changes in differentially expressed proteins in broilers with different growth performances using liver tissue from 35-day-old chickens (Ross-308). Changes in protein levels were analyzed with two-dimensional gel electrophoresis (2DE) and mass spectrometry. This study contained 2 groups (control and heat treatment groups) with 8 replicates per group. After d 20, ten birds were assigned to each replicate. On d 35, the heat treatment group was subdivided into 2 groups, a heat stressed high body weight group (HH) and a heat stressed low body weight group (HL). Body weight was lower in the heat treatment group than that in the control group. In the heat treatment group, the HH group had a significantly higher body weight than the HL group. The expression of heat shock protein 70 significantly increased in the HL group. Protein spots with significant differences in 2DE analysis were screened and selected. Thirteen significant spots were excised and analyzed using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF). Among the 13 spots, 8 spots were identified. The identified spots were MRP-126, fatty acid binding protein, ferritin heavy chain, glutathione S-transferase, agmatinase; mitochondrial, alpha-enolase, 60 kDa heat shock protein; mitochondrial, and tubulin beta-7 chain. Our study has showed that high temperature stress aggravated oxidative stress in broilers, which resulted in comparatively slow growth to preserve body homeostasis.

Cryopreservation and post-thaw characterization of dissociated human islet cells

The objective of this study is to optimize the cryopreservation of dissociated islet cells and obtain functional cells that can be used in single-cell transcriptome studies on the pathology and treatment of diabetes. Using an iterative graded freezing approach we obtained viable cells after cooling in 10% dimethyl sulfoxide and 6% hydroxyethyl starch at 1°C/min to -40°C, storage in liquid nitrogen, rapid thaw, and removal of cryoprotectants by serial dilution. The expression of epithelial cell adhesion molecule declined immediately after thaw, but recovered after overnight incubation, while that of an endocrine cell marker (HPi2) remained high after cryopreservation. Patch-clamp electrophysiology revealed differences in channel activities and exocytosis of various islet cell types; however, exocytotic responses, and the biophysical properties of voltage-gated Na+ and Ca2+ channels, are sustained after cryopreservation. Single-cell RNA sequencing indicates that overall transcriptome and crucial exocytosis genes are comparable between fresh and cryopreserved dispersed human islet cells. Thus, we report an optimized procedure for cryopreserving dispersed islet cells that maintained their membrane integrity, along with their molecular and functional phenotypes. Our findings will not only provide a ready source of cells for investigating cellular mechanisms in diabetes but also for bio-engineering pseudo-islets and islet sheets for modeling studies and potential transplant applications.

Uncovering the Metabolic and Stress Responses of Human Embryonic Stem Cells to FTH1 Gene Silencing

Embryonic stem cells (ESCs) are pluripotent cells with indefinite self-renewal ability and differentiation properties. To function properly and maintain genomic stability, ESCs need to be endowed with an efficient repair system as well as effective redox homeostasis. In this study, we investigated different aspects involved in ESCs' response to iron accumulation following stable knockdown of the ferritin heavy chain (FTH1) gene, which encodes for a major iron storage protein with ferroxidase activity. Experimental findings highlight unexpected and, to a certain extent, paradoxical results. If on one hand FTH1 silencing does not correlate with increased ROS production nor with changes in the redox status, strengthening the concept that hESCs are extremely resistant and, to a certain extent, even refractory to intracellular iron imbalance, on the other, the differentiation potential of hESCs seems to be affected and apoptosis is observed. Interestingly, we found that FTH1 silencing is accompanied by a significant activation of the nuclear factor (erythroid-derived-2)-like 2 (Nrf2) signaling pathway and pentose phosphate pathway (PPP), which crosstalk in driving hESCs antioxidant cascade events. These findings shed new light on how hESCs perform under oxidative stress, dissecting the molecular mechanisms through which Nrf2, in combination with PPP, counteracts oxidative injury triggered by FTH1 knockdown.

The Retina in Patients With Triple A Syndrome: A Window Into Neurodegeneration?

OBJECTIVE

Experimental evidence suggests that the clinical manifestations of Triple A syndrome result from oxidative stress. Several conditions caused by oxidative stress display retinal involvement. Our objective was to assess the retina and optic nerve involvement in children with Triple A syndrome.

METHODS

Eleven patients with genetically proven Triple A syndrome followed-up in our centre were approached for study participation. The main outcome was the measurement of the thicknesses of the different retinal layers by Optical Coherence Tomography (OCT).

RESULTS

9 patients with triple A syndrome had OCT measurements. 7 patients were children and 2 were adults; 4 were females and 5 were males. The 7 paediatric patients had at least two OCT measured at a mean interval of 7.9 months after the first one. The average Retinal Nerve Fibre Layer thickness was 74 ± 10 µm in patients compared to the paediatric reference range of 100 ± 2 µm (p<0.05).

CONCLUSIONS AND RELEVANCE

This is the first study to document retinal layer thicknesses in a series of patients with Triple A syndrome. Nearly all retinal thickness and peripapillary RNFL measurements were very significantly inferior to the reference range in Triple A patients, whatever their age. RNFL thinning was more marked at the temporal part of the optic nerve. OCT being non-invasive, it represents a promising tool to assess the severity of neurodegeneration in patients with Triple A syndrome.

FTH1 Pseudogenes in Cancer and Cell Metabolism

Ferritin, the principal intracellular iron-storage protein localized in the cytoplasm, nucleus, and mitochondria, plays a major role in iron metabolism. The encoding ferritin genes are members of a multigene family that includes some pseudogenes. Even though pseudogenes have been initially considered as relics of ancient genes or junk DNA devoid of function, their role in controlling gene expression in normal and transformed cells has recently been re-evaluated. Numerous studies have revealed that some pseudogenes compete with their parental gene for binding to the microRNAs (miRNAs), while others generate small interference RNAs (siRNAs) to decrease functional gene expression, and still others encode functional mutated proteins. Consequently, pseudogenes can be considered as actual master regulators of numerous biological processes. Here, we provide a detailed classification and description of the structural features of the ferritin pseudogenes known to date and review the recent evidence on their mutual interrelation within the complex regulatory network of the ferritin gene family.

WD40-Repeat Proteins in Ciliopathies and Congenital Disorders of Endocrine System

WD40-repeat (WDR)-containing proteins constitute an evolutionarily conserved large protein family with a broad range of biological functions. In human proteome, WDR makes up one of the most abundant protein-protein interaction domains. Members of the WDR protein family play important roles in nearly all major cellular signalling pathways. Mutations of WDR proteins have been associated with various human pathologies including neurological disorders, cancer, obesity, ciliopathies and endocrine disorders. This review provides an updated overview of the biological functions of WDR proteins and their mutations found in congenital disorders. We also highlight the significant role of WDR proteins in ciliopathies and endocrine disorders. The new insights may help develop therapeutic approaches targeting WDR motifs.

Two novel truncating variants of the AAAS gene causative of the triple A syndrome

PURPOSE

The triple A syndrome (AAAS) is an inherited condition associated with mutations in the AAAS gene, which encodes a protein of 546 amino acids known as ALADIN (alacrima achalasia adrenal insufficiency neurologic disorder) whose function is not well understood. This protein belongs to the WD-repeat family of regulatory proteins and is located in the nuclear pore complexes. Only a few cohorts of AAAS patients have been reported and fully characterized. Thus, the objective of the present study was to report on a mini cohort of Italian AAAS patients and to get insights on their predisposing genetic defects.

METHODS

Genetic analysis of AAAS gene in triple A syndrome patient and molecular and functional characterization of the novel identified allelic variants.

RESULTS

Here we describe three newly diagnosed cases of AAAS, in whom genetic analysis allowed us to identify two novel allelic variants in the AAAS gene: the frameshift substitution c.765 dupT (p.Gly256Trp fsX67) in exon 8 and the splice site mutation in intron 11(c.997-2 A > G, IVS11-2A > G). Both variants result in a truncated non-functional protein, as we demonstrate by transcript analysis and expression studies.

CONCLUSIONS

Our findings establish a pathogenic role for both new variants. Moreover, our data highlight the essential role of the C-terminal domain of the protein for its correct targeting and function and underline the importance of sequencing splice sites surrounding the intron-exon junctions to ensure accurate molecular diagnosis and correct genetic counseling in AAAS patients.

A broad range of symptoms in allgrove syndrome: single center experience in Southeast Anatolia

BACKGROUND

Allgrove syndrome (OMIM 231550) is a rare autosomal recessive disease characterized by non-CAH primary adrenal insufficiency (non-CAH PAI), alacrima, and achalasia. It is caused by mutations in the AAAS gene. The syndrome is also associated with variable progressive neurological impairment and dermatological abnormalities.

METHODS AND RESULTS

We diagnosed 23 patients from 14 families with Allgrove syndrome, based on the presence of at least two characteristic symptoms, usually adrenal insufficiency and alacrima, between 2008 and 2018. A previously described nonsense variant of AAAS was detected in 19 patients from 12 families at homozygous state. Another novel homozygous mutation (c.394-397delCTGT) in AAAS was detected in four patients from two families. Presenting symptoms were alacrima (23/23; 100%), adrenal insufficiency (18/23; 78%), achalasia (13/23; 57%), short stature/growth retardation (16/23; 70%), hyperreflexia (15/23; 65%), palmoplantar hyperkeratosis (13/23; 57%), hyperpigmentation of the skin (10/23; 43%), hypoglycemia-induced convulsion (7/23; 30%), swallowing difficulty and vomiting (6/23; 26%). Serum DHEAS concentrations were low in all patients (23/23; 100%).

CONCLUSIONS

Clinical symptoms vary even among patients carrying the same mutation. Triple A syndrome should be considered in the etiology of non-CAH PAI in Arab populations and in Southeast Turkey. Any child with non-CAH PAI should be evaluated for the presence of alacrima and/or achalasia or family history of alacrima and/or achalasia. Children with alacrima and/or achalasia should also be investigated for adrenal insufficiency. Definitive molecular diagnosis is essential for early diagnosis and management of adrenal insufficiency, neurological symptoms, and growth retardation in patients and early diagnosis of as yet asymptomatic cases in the family, together with genetic counseling.

Morphine-Induced Modulation of Endolysosomal Iron Mediates Upregulation of Ferritin Heavy Chain in Cortical Neurons

HIV-associated neurocognitive disorders (HAND) remain prevalent and are aggravated by µ-opioid use. We have previously shown that morphine and other µ-opioids may contribute to HAND by inhibiting the homeostatic and neuroprotective chemokine receptor CXCR4 in cortical neurons, and this novel mechanism depends on upregulation of the protein ferritin heavy chain (FHC). Here, we examined the cellular events and potential mechanisms involved in morphine-mediated FHC upregulation using rat cortical neurons of either sex in vitro and in vivo. Morphine dose dependently increased FHC protein levels in primary neurons through µ-opioid receptor (µOR) and Gαi-protein signaling. Cytoplasmic FHC levels were significantly elevated, but nuclear FHC levels and FHC gene expression were unchanged. Morphine-treated rats also displayed increased FHC levels in layer 2/3 neurons of the prefrontal cortex. Importantly, both in vitro and in vivo FHC upregulation was accompanied by loss of mature dendritic spines, which was also dependent on µOR and Gαi-protein signaling. Moreover, morphine upregulated ferritin light chain (FLC), a component of the ferritin iron storage complex, suggesting that morphine altered neuronal iron metabolism. Indeed, prior to FHC upregulation, morphine increased cytoplasmic labile iron levels as a function of decreased endolysosomal iron. In line with this, chelation of endolysosomal iron (but not extracellular iron) blocked morphine-induced FHC upregulation and dendritic spine reduction, whereas iron overloading mimicked the effect of morphine on FHC and dendritic spines. Overall, these data demonstrate that iron mediates morphine-induced FHC upregulation and consequent dendritic spine deficits and implicate endolysosomal iron efflux to the cytoplasm in these effects.

Primary adrenal insufficiency in children: Diagnosis and management

Primary adrenal insufficiency (PAI) is a life-threatening disorder of adrenal cortex which is characterized by deficient biosynthesis of glucocorticoids, with or without deficiency in mineralocorticoids and adrenal androgens. Typical manifestations of primary adrenal insufficiency include hyperpigmentation, hypotension, hypoglycaemia, hyponatremia with or without hyperkalemia that are generally preceded by nonspecific symptoms at the onset. Recessively inherited monogenic disorders constitute the largest group of primary adrenal insufficiency in children. The diagnostic process of primary adrenal insufficiency includes demonstration of low cortisol concentrations along with high plasma ACTH and identifying the cause of the disorder. Specific molecular diagnosis is achieved in more than 80% of children with PAI by detailed clinical and biochemical characterization integrated with advanced molecular tools. Hormone replacement therapy determined on the type and the severity of deficient adrenocortical hormones is the mainstay of treatment. Optimized methods of steroid hormone delivery, improved monitoring of hormone replacement along with intensive education of patients and families on the rules during intercurrent illness and stress will significantly reduce the morbidity and mortality associated with primary adrenal insufficiency.

FHC, an NS4B-interacting Protein, Enhances Classical Swine Fever Virus Propagation and Acts Positively in Viral Anti-apoptosis

Classical swine fever virus (CSFV), the etiological agent of classical swine fever, causes enormous economic loss to the pig industry. Ferritin heavy chain (FHC) is a notable anti-apoptotic protein, and existing evidence suggests that CSFV cannot induce apoptosis of host cells, however, the role of FHC in CSFV replication remains unclear. In the present study, we found that recombinant lentivirus-mediated knockdown or overexpression of FHC inhibited or enhanced CSFV replication, respectively, indicating a positive role for FHC in CSFV proliferation. Furthermore, interaction between the CSFV NS4B protein and FHC was confirmed by glutathione S-transferase (GST) pull-down, co-immunoprecipitation (co-IP) and confocal imaging assays. In addition, both CSFV replication and NS4B expression upregulated expression of FHC, which counteracts apoptosis by modulating cellular reactive oxygen species (ROS). These results suggest that FHC, an NS4B-interacting protein, enhances CSFV replication and has a positive role in viral anti-apoptosis by regulating ROS accumulation. This work may provide a new perspective for understanding the mechanism of CSFV pathogenesis.

Triple-A syndrome: a wide spectrum of adrenal dysfunction

OBJECTIVE

Triple-A or Allgrove syndrome is an autosomal recessive disorder due to mutations in the AAAS gene, which encodes a nucleoporin named ALADIN. It is characterized by a classical clinical triad: alacrima, achalasia and adrenal insufficiency, the canonic symptoms that are associated with progressive peripheral neuropathy. Only a few cohorts have been reported. The objective of the present study was to characterize the various spectra of adrenal function in Triple-A patients.

METHODS

A retrospective clinical and biological monitoring of 14 patients (10 families) was done in a single multidisciplinary French center. All had AAAS gene sequenced and adrenal function evaluation.

RESULTS

Nine different AAAS mutations were found, including one new mutation: c.755G>C, p.(Trp252Ser). Regarding adrenal function, defects of the zona fasciculata and reticularis were demonstrated by increased basal ACTH levels and low DHEAS levels in all cases regardless of the degree of glucocorticoid deficiency. In contrast, mineralocorticoid function was always conserved: i.e., normal plasma renin level associated with normal aldosterone level. The main prognostic feature was exacerbation of neuropathy and cognitive disorders.

CONCLUSIONS

These data suggest that, in Triple-A patients, adrenal function can be deficient, insufficient or compensated. In our cohort after the first decade of life, there does not appear to be any degradation of adrenal function over time. However, patients with compensated adrenal function should be informed and educated to manage a glucocorticoid replacement therapy in case of stressful conditions, with no need for systematic long-term treatment.

Clinical and genetic characterisation of a series of patients with triple A syndrome

Triple A syndrome (TAS) or Allgrove syndrome (OMIM #231550) is a rare autosomal recessive disorder characterised by adrenocorticotropic hormone-resistant adrenal insufficiency, alacrima, achalasia, and neurological and dermatological abnormalities. Mutations in the AAAS gene on chromosome 12q13 encoding the nuclear pore protein ALADIN have been reported in these patients. Between 2006 and 2017, we evaluated six patients with a clinical diagnosis of TAS, based on the presence of at least two symptoms, usually adrenal insufficiency and alacrima. In all cases, genetic analysis revealed homozygous mutations in the AAAS gene. One novel mutation was detected: a homozygous 10-bp deletion (c.1264_1273del, p.Q422NfsX126) in exon 14 of the AAAS gene that caused a frameshift that introduced an aberrant stop codon after 126 amino acids. This genetic variant is likely to be pathogenic because it caused a significant change in protein structure. A precise genotype-phenotype correlation was impossible to establish.

CONCLUSIONS

Based on our experience, we recommend that molecular analysis should be performed in the presence of alacrima and at least one more symptom of TAS. Our cases share many clinical features of TAS and underline the variability in this syndrome, as well as the need for thorough investigation following a multidisciplinary approach. What is known: • Triple A syndrome is characterised by achalasia, alacrima, adrenal insufficiency, neurological impairment, and dermatological abnormalities. • A precise genotype-phenotype correlation has proved impossible to establish. What is new: • These cases add to a large number of similar case reports with limited novel information. • The newly identified AAAS gene mutation was reported.

Compensation for chronic oxidative stress in ALADIN null mice

Mutations in the AAAS gene coding for the nuclear pore complex protein ALADIN lead to the autosomal recessive disorder triple A syndrome. Triple A patients present with a characteristic phenotype including alacrima, achalasia and adrenal insufficiency. Patient fibroblasts show increased levels of oxidative stress, and several in vitro studies have demonstrated that the nucleoporin ALADIN is involved in both the cellular oxidative stress response and adrenal steroidogenesis. It is known that ALADIN knock-out mice lack a phenotype resembling human triple A syndrome. The objective of this study was to determine whether the application of chronic oxidative stress by ingestion of paraquat would generate a triple A-like phenotype in ALADIN null mice. Adult male mice were fed either a paraquat (0.25 g/kg diet) or control diet for 11 days. After application of chronic oxidative stress, ALADIN knock-out mice presented with an unexpected compensated glutathione metabolism, but lacked a phenotype resembling human triple A syndrome. We did not observe increased levels of oxidative stress and alterations in adrenal steroidogenesis in mice depleted for ALADIN. This study stresses the species-specific role of the nucleoporin ALADIN, which in mice involves a novel compensatory mechanism for regulating the cellular glutathione redox response.

Summary: ALADIN knock-out mice present with an unexpected compensated metabolism of glutathione after application of chronic oxidative stress, whilst lacking a phenotype resembling human triple A syndrome.

ALADIN is required for the production of fertile mouse oocytes

The nucleoporin ALADIN is required for multiple stages of oocyte maturation and for supporting embryonic divisions postfertilization.

Asymmetric cell divisions depend on the precise placement of the spindle apparatus. In mammalian oocytes, spindles assemble close to the cell’s center, but chromosome segregation takes place at the cell periphery where half of the chromosomes are expelled into small, nondeveloping polar bodies at anaphase. By dividing so asymmetrically, most of the cytoplasmic content within the oocyte is preserved, which is critical for successful fertilization and early development. Recently we determined that the nucleoporin ALADIN participates in spindle assembly in somatic cells, and we have also shown that female mice homozygously null for ALADIN are sterile. In this study we show that this protein is involved in specific meiotic stages, including meiotic resumption, spindle assembly, and spindle positioning. In the absence of ALADIN, polar body extrusion is compromised due to problems in spindle orientation and anchoring at the first meiotic anaphase. ALADIN null oocytes that mature far enough to be fertilized in vitro are unable to support embryonic development beyond the two-cell stage. Overall, we find that ALADIN is critical for oocyte maturation and appears to be far more essential for this process than for somatic cell divisions.

The roles of the nuclear pore complex in cellular dysfunction, aging and disease

The study of the Nuclear Pore Complex (NPC), the proteins that compose it (nucleoporins), and the nucleocytoplasmic transport that it controls have revealed an unexpected layer to pathogenic disease onset and progression. Recent advances in the study of the regulation of NPC composition and function suggest that the precise control of this structure is necessary to prevent diseases from arising or progressing. Here we discuss the role of nucleoporins in a diverse set of diseases, many of which directly or indirectly increase in occurrence and severity as we age, and often shorten the human lifespan. NPC biology has been shown to play a direct role in these diseases and therefore in the process of healthy aging.

Ferritin heavy polypeptide 1 mediates apoptosis-related gene expression of duck (Anas platyrhynchos domesticus)

Duck hepatitis virus type 1 (DHV-1) infection of ducklings causes hepatitis and is associated with high morbidity and mortality. Virus infection may induce apoptosis and inhibit proliferation. In humans, ferritin heavy polypeptide 1 (FTH1) has been reported to affect the development of hepatitis and inhibit apoptosis. However, the effect of duck FTH1 (duFTH1) on apoptosis in DHV-1 infected ducklings has not been investigated. Therefore, we measured duFHT1 expression in tissues of DHV-1 infected ducklings and characterized the functional effects of ectopic overexpression and endogenous downregulation of FTH1 in duck embryo fibroblasts (DEF) to elucidate possible mechanisms involved. In the present study, the expression of duFTH1 was decreased in liver and spleen after DHV-1 infection. The effects of altered FTH1 expression on expression of pro- and anti-apoptotic genes were evaluated by qPCR arrays. Decreased expressions of Caspase-3 and Caspase-8 were observed in FTH1-overexpressing DEF cells, while decreased expression of Bcl-2 was detected in FTH1 knocked down DEF cells. Our findings suggest that the regulation of FTH1 expression indirectly mediated the expression of apoptosis-related genes; the protective effect of FTH1 was associated with the inhibition of apoptosis in DEF.

Identification of a novel putative interaction partner of the nucleoporin ALADIN

It has been shown that the nucleoporin ALADIN plays a significant role in the redox homeostasis of the cell, but its function in steroidogenesis contributing to adrenal atrophy in triple A syndrome remains largely unknown. In an attempt to identify new interaction partners of ALADIN, co-immunoprecipitation followed by proteome analysis was conducted in different expression models using the human adrenocortical tumour cell line NCI-H295R. Our results suggest an interaction of ALADIN with the microsomal protein PGRMC2. PGRMC2 is shown to be activity regulator of CYP P450 enzymes and, therefore, to be a possible target for adrenal dysregulation in triple A syndrome. We show that there is a sexual dimorphism regarding the expression of Pgrmc2 in adrenals and gonads of wild-type (WT) and Aaas knock-out (KO) mice. Female Aaas KO mice are sterile due to delayed oocyte maturation and meiotic spindle assembly. A participation in meiotic spindle assembly confirms the recently investigated involvement of ALADIN in mitosis and emphasises an interaction with PGRMC2 which is a regulator of the cell cycle. By identification of a novel interaction partner of ALADIN, we provide novel aspects for future research of the function of ALADIN during cell cycle and for new insights into the pathogenesis of triple A syndrome.

Nucleoporin genes in human diseases

Nuclear pore complexes (NPCs) are large channels spanning the nuclear envelope that mediate nucleocytoplasmic transport. They are composed of multiple copies of ~30 proteins termed nucleoporins (NUPs). Alterations in NUP genes are linked to several human neoplastic and non-neoplastic diseases. This review focuses on NUPs, their genes, localization, function in the NPC and involvement in human diseases.

Nuclear Pore Complexes and Nucleocytoplasmic Transport: From Structure to Function to Disease

Nucleocytoplasmic transport is an essential cellular activity and occurs via nuclear pore complexes (NPCs) that reside in the double membrane of the nuclear envelope. Significant progress has been made during the past few years in unravelling the ultrastructural organization of NPCs and their constituents, the nucleoporins, by cryo-electron tomography and X-ray crystallography. Mass spectrometry and genomic approaches have provided deeper insight into the specific regulation and fine tuning of individual nuclear transport pathways. Recent research has also focused on the roles nucleoporins play in health and disease, some of which go beyond nucleocytoplasmic transport. Here we review emerging results aimed at understanding NPC architecture and nucleocytoplasmic transport at the atomic level, elucidating the specific function individual nucleoporins play in nuclear trafficking, and finally lighting up the contribution of nucleoporins and nuclear transport receptors in human diseases, such as cancer and certain genetic disorders.

The nucleoporin ALADIN regulates Aurora A localization to ensure robust mitotic spindle formation

The nucleoporin ALADIN, which is mutated in patients with triple A syndrome, is necessary for proper spindle formation. Without ALADIN, active Aurora A moves away from centrosomes. The relocalization of active Aurora A leads to a redistribution of specific spindle assembly factors that make spindles less stable and slows their formation.

The formation of the mitotic spindle is a complex process that requires massive cellular reorganization. Regulation by mitotic kinases controls this entire process. One of these mitotic controllers is Aurora A kinase, which is itself highly regulated. In this study, we show that the nuclear pore protein ALADIN is a novel spatial regulator of Aurora A. Without ALADIN, Aurora A spreads from centrosomes onto spindle microtubules, which affects the distribution of a subset of microtubule regulators and slows spindle assembly and chromosome alignment. ALADIN interacts with inactive Aurora A and is recruited to the spindle pole after Aurora A inhibition. Of interest, mutations in ALADIN cause triple A syndrome. We find that some of the mitotic phenotypes that we observe after ALADIN depletion also occur in cells from triple A syndrome patients, which raises the possibility that mitotic errors may underlie part of the etiology of this syndrome.

Recessive nephrocerebellar syndrome on the Galloway-Mowat syndrome spectrum is caused by homozygous protein-truncating mutations of WDR73

Galloway-Mowat syndrome (GMS) is a neurodevelopmental disorder characterized by microcephaly, cerebellar hypoplasia, nephrosis, and profound intellectual disability. Jinks et al. extend the GMS spectrum by identifying a novel nephrocerebellar syndrome with selective striatal cholinergic interneuron loss and complete lateral geniculate nucleus delamination, caused by a frameshift mutation in WDR73.

We describe a novel nephrocerebellar syndrome on the Galloway-Mowat syndrome spectrum among 30 children (ages 1.0 to 28 years) from diverse Amish demes. Children with nephrocerebellar syndrome had progressive microcephaly, visual impairment, stagnant psychomotor development, abnormal extrapyramidal movements and nephrosis. Fourteen died between ages 2.7 and 28 years, typically from renal failure. Post-mortem studies revealed (i) micrencephaly without polymicrogyria or heterotopia; (ii) atrophic cerebellar hemispheres with stunted folia, profound granule cell depletion, Bergmann gliosis, and signs of Purkinje cell deafferentation; (iii) selective striatal cholinergic interneuron loss; and (iv) optic atrophy with delamination of the lateral geniculate nuclei. Renal tissue showed focal and segmental glomerulosclerosis and extensive effacement and microvillus transformation of podocyte foot processes. Nephrocerebellar syndrome mapped to 700 kb on chromosome 15, which contained a single novel homozygous frameshift variant (WDR73 c.888delT; p.Phe296Leufs*26). WDR73 protein is expressed in human cerebral cortex, hippocampus, and cultured embryonic kidney cells. It is concentrated at mitotic microtubules and interacts with α-, β-, and γ-tubulin, heat shock proteins 70 and 90 (HSP-70; HSP-90), and the carbamoyl phosphate synthetase 2/aspartate transcarbamylase/dihydroorotase multi-enzyme complex. Recombinant WDR73 p.Phe296Leufs*26 and p.Arg256Profs*18 proteins are truncated, unstable, and show increased interaction with α- and β-tubulin and HSP-70/HSP-90. Fibroblasts from patients homozygous for WDR73 p.Phe296Leufs*26 proliferate poorly in primary culture and senesce early. Our data suggest that in humans, WDR73 interacts with mitotic microtubules to regulate cell cycle progression, proliferation and survival in brain and kidney. We extend the Galloway-Mowat syndrome spectrum with the first description of diencephalic and striatal neuropathology.

Role of ALADIN in human adrenocortical cells for oxidative stress response and steroidogenesis

Triple A syndrome is caused by mutations in AAAS encoding the protein ALADIN. We investigated the role of ALADIN in the human adrenocortical cell line NCI-H295R1 by either over-expression or down-regulation of ALADIN. Our findings indicate that AAAS knock-down induces a down-regulation of genes coding for type II microsomal cytochrome P450 hydroxylases CYP17A1 and CYP21A2 and their electron donor enzyme cytochrome P450 oxidoreductase, thereby decreasing biosynthesis of precursor metabolites required for glucocorticoid and androgen production. Furthermore we demonstrate that ALADIN deficiency leads to increased susceptibility to oxidative stress and alteration in redox homeostasis after paraquat treatment. Finally, we show significantly impaired nuclear import of DNA ligase 1, aprataxin and ferritin heavy chain 1 in ALADIN knock-down cells. We conclude that down-regulating ALADIN results in decreased oxidative stress response leading to alteration in steroidogenesis, highlighting our knock-down cell model as an important in-vitro tool for studying the adrenal phenotype in triple A syndrome.

Quantitative proteomic analysis of synovial tissue from rats with collagen-induced arthritis

The pathway networks involved in RA pathological process were analyzed by Ingenuity pathway analysis (IPA).

Serum ferritin is an important inflammatory disease marker, as it is mainly a leakage product from damaged cells

"Serum ferritin" presents a paradox, as the iron storage protein ferritin is not synthesised in serum yet is to be found there. Serum ferritin is also a well known inflammatory marker, but it is unclear whether serum ferritin reflects or causes inflammation, or whether it is involved in an inflammatory cycle. We argue here that serum ferritin arises from damaged cells, and is thus a marker of cellular damage. The protein in serum ferritin is considered benign, but it has lost (i.e. dumped) most of its normal complement of iron which when unliganded is highly toxic. The facts that serum ferritin levels can correlate with both disease and with body iron stores are thus expected on simple chemical kinetic grounds. Serum ferritin levels also correlate with other phenotypic readouts such as erythrocyte morphology. Overall, this systems approach serves to explain a number of apparent paradoxes of serum ferritin, including (i) why it correlates with biomarkers of cell damage, (ii) why it correlates with biomarkers of hydroxyl radical formation (and oxidative stress) and (iii) therefore why it correlates with the presence and/or severity of numerous diseases. This leads to suggestions for how one might exploit the corollaries of the recognition that serum ferritin levels mainly represent a consequence of cell stress and damage.

Thioredoxin Reductase 2 (TXNRD2) mutation associated with familial glucocorticoid deficiency (FGD)

CONTEXT

Classic ACTH resistance, due to disruption of ACTH signaling, accounts for the majority of cases of familial glucocorticoid deficiency (FGD). Recently FGD cases caused by mutations in the mitochondrial antioxidant, nicotinamide nucleotide transhydrogenase, have highlighted the importance of redox regulation in steroidogenesis.

OBJECTIVE

We hypothesized that other components of mitochondrial antioxidant systems would be good candidates in the etiology of FGD.

DESIGN

Whole-exome sequencing was performed on three related patients, and segregation of putative causal variants confirmed by Sanger sequencing of all family members. A TXNRD2-knockdown H295R cell line was created to investigate redox homeostasis.

SETTING

The study was conducted on patients from three pediatric centers in the United Kingdom.

PATIENTS

Seven individuals from a consanguineous Kashmiri kindred, six of whom presented with FGD between 0.1 and 10.8 years, participated in the study.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURE

Identification and functional interrogation of a novel homozygous mutation segregating with the disease trait were measured.

RESULTS

A stop gain mutation, p.Y447X in TXNRD2, encoding the mitochondrial selenoprotein thioredoxin reductase 2 (TXNRD2) was identified and segregated with disease in this extended kindred. RT-PCR and Western blotting revealed complete absence of TXNRD2 in patients homozygous for the mutation. TXNRD2 deficiency leads to impaired redox homeostasis in a human adrenocortical cell line.

CONCLUSION

In contrast to the Txnrd2-knockout mouse model, in which embryonic lethality as a consequence of hematopoietic and cardiac defects is described, absence of TXNRD2 in humans leads to glucocorticoid deficiency. This is the first report of a homozygous mutation in any component of the thioredoxin antioxidant system leading to inherited disease in humans.

Oxidative stress and adrenocortical insufficiency

Maintenance of redox balance is essential for normal cellular functions. Any perturbation in this balance due to increased reactive oxygen species (ROS) leads to oxidative stress and may lead to cell dysfunction/damage/death. Mitochondria are responsible for the majority of cellular ROS production secondary to electron leakage as a consequence of respiration. Furthermore, electron leakage by the cytochrome P450 enzymes may render steroidogenic tissues acutely vulnerable to redox imbalance. The adrenal cortex, in particular, is well supplied with both enzymatic (glutathione peroxidases and peroxiredoxins) and non-enzymatic (vitamins A, C and E) antioxidants to cope with this increased production of ROS due to steroidogenesis. Nonetheless oxidative stress is implicated in several potentially lethal adrenal disorders including X-linked adrenoleukodystrophy, triple A syndrome and most recently familial glucocorticoid deficiency. The finding of mutations in antioxidant defence genes in the latter two conditions highlights how disturbances in redox homeostasis may have an effect on adrenal steroidogenesis.

Deficiency of ALADIN impairs redox homeostasis in human adrenal cells and inhibits steroidogenesis

Triple A syndrome is a rare, autosomal recessive cause of adrenal failure. Additional features include alacrima, achalasia of the esophageal cardia, and progressive neurodegenerative disease. The AAAS gene product is the nuclear pore complex protein alacrima-achalasia-adrenal insufficiency neurological disorder (ALADIN), of unknown function. Triple A syndrome patient dermal fibroblasts appear to be more sensitive to oxidative stress than wild-type fibroblasts. To provide an adrenal and neuronal-specific disease model, we established AAAS-gene knockdown in H295R human adrenocortical tumor cells and SH-SY5Y human neuroblastoma cells by lentiviral short hairpin RNA transduction. AAAS-knockdown significantly reduced cell viability in H295R cells. This effect was exacerbated by hydrogen peroxide treatment and improved by application of the antioxidant N-acetylcysteine. An imbalance in redox homeostasis after AAAS knockdown was further suggested in the H295R cells by a decrease in the ratio of reduced to oxidized glutathione. AAAS-knockdown SH-SY5Y cells were also hypersensitive to oxidative stress and responded to antioxidant treatment. A further impact on function was observed in the AAAS-knockdown H295R cells with reduced expression of key components of the steroidogenic pathway, including steroidogenic acute regulatory and P450c11β protein expression. Importantly a significant reduction in cortisol production was demonstrated with AAAS knockdown, which was partially reversed with N-acetylcysteine treatment.

CONCLUSION

Our in vitro data in AAAS-knockdown adrenal and neuronal cells not only corroborates previous studies implicating oxidative stress in this disorder but also provides further insights into the pathogenic mechanisms in triple A syndrome.

Familial glucocorticoid deficiency: New genes and mechanisms

Familial Glucocorticoid deficiency (FGD), in which the adrenal cortex fails to produce glucocorticoids, was first shown to be caused by defects in the receptor for ACTH (MC2R) or its accessory protein (MRAP). Certain mutations in the steroidogenic acute regulatory protein (STAR) can also masquerade as FGD. Recently mutations in mini chromosome maintenance-deficient 4 homologue (MCM4) and nicotinamide nucleotide transhydrogenase (NNT), genes involved in DNA replication and antioxidant defence respectively, have been recognised in FGD cohorts. These latest findings expand the spectrum of pathogenetic mechanisms causing adrenal disease and imply that the adrenal may be hypersensitive to replicative and oxidative stresses. Over time patients with MCM4 or NNT mutations may develop other organ pathologies related to their impaired gene functions and will therefore need careful monitoring.

Genes for iron metabolism influence circadian rhythms in Drosophila melanogaster

Haem has been previously implicated in the function of the circadian clock, but whether iron homeostasis is integrated with circadian rhythms is unknown. Here we describe an RNA interference (RNAi) screen using clock neurons of Drosophila melanogaster. RNAi is targeted to iron metabolism genes, including those involved in haem biosynthesis and degradation. The results indicate that Ferritin 2 Light Chain Homologue (Fer2LCH) is required for the circadian activity of flies kept in constant darkness. Oscillations of the core components in the molecular clock, PER and TIM, were also disrupted following Fer2LCH silencing. Other genes with a putative function in circadian biology include Transferrin-3, CG1358 (which has homology to the FLVCR haem export protein) and five genes implicated in iron-sulfur cluster biosynthesis: the Drosophila homologues of IscS (CG12264), IscU (CG9836), IscA1 (CG8198), Iba57 (CG8043) and Nubp2 (CG4858). Therefore, Drosophila genes involved in iron metabolism are required for a functional biological clock.

The genetic basis of triple A (Allgrove) syndrome in a Greek family

Triple A (or Allgrove) syndrome is an autosomal recessive genetic disorder. Patients typically suffer from chronic adrenal insufficiency due to resistance to ACTH (Addison's disease), achalasia of the cardia, and defective tear formation (alacrima). The syndrome is caused by mutations in the AAAS gene which encodes the protein ALADIN, a constituent of eukaryotic nuclear pore complexes. The multi-systemic nature and variable manifestations of the triple A syndrome often confound its diagnosis and limit our understanding of its exact pathogenesis. We performed mutational screening of the AAAS gene in a Greek family of four individuals, including an affected propositus with typical symptoms of late-onset triple A syndrome. Our results are consistent with an autosomal recessive pattern of inheritance within the family, caused by a functional c.43C>A mutation in exon 1 of the AAAS gene. All members of the family were also homozygous for a silent c.855C>T nucleotide change within exon 9 of the AAAS gene, representing a common single nucleotide polymorphism. The compromising c.43C>A mutation is predicted to cause a p.Gln15Lys amino acid substitution in the ALADIN protein. However, it has been suggested that the functional impact of this mutation may be more severe, causing a shift in the reading frame of AAAS gene via formation of an aberrant premature donor splice site within exon 1. We propose that mutational analysis of the AAAS gene should be considered in adult patients with one or more clinical signs of the disease, as diagnosis of late-onset cases can be ambiguous.

Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency

Using targeted exome sequencing, we identified mutations in NNT, an antioxidant defense gene, in individuals with familial glucocorticoid deficiency. In mice with Nnt loss, higher levels of adrenocortical cell apoptosis and impaired glucocorticoid production were observed. NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels. Our results suggest that NNT may have a role in ROS detoxification in human adrenal glands.

Neurologic presentation of triple A syndrome

"Triple A" syndrome is a rare, autosomal recessive condition whose main clinical features are alacrima, achalasia, and adrenal failure. Most patients also develop some neurologic abnormalities. We describe an 11-year-old boy with triple A syndrome who presented with progressive axonal motor neuropathy. Molecular analysis revealed compound heterozygous mutations in the AAAS gene, confirming the clinical diagnosis. The clinical presentation of patients with triple A syndrome is variable. Our patient manifested neurologic problems during early childhood, before other features of this condition were apparent. We highlight the neurologic presentation of this multisystem disorder. In the presence of complex axonal neuropathy, other features of this condition should be sought.

Regulation of neuronal ferritin heavy chain, a new player in opiate-induced chemokine dysfunction

The heavy chain subunit of ferritin (FHC), a ubiquitous protein best known for its iron-sequestering activity as part of the ferritin complex, has recently been described as a novel inhibitor of signaling through the chemokine receptor CXCR4. Levels of FHC as well as its effects on CXCR4 activation increase in cortical neurons exposed to mu-opioid receptor agonists such as morphine, an effect likely specific to neurons. Major actions of CXCR4 signaling in the mature brain include a promotion of neurogenesis, activation of pro-survival signals, and modulation of excitotoxic pathways; thus, FHC up-regulation may contribute to the neuronal dysfunction often associated with opiate drug abuse. This review summarizes our knowledge of neuronal CXCR4 function, its regulation by opiates and the role of FHC in this process, and known mechanisms controlling FHC production. We speculate on the mechanism involved in FHC regulation by opiates and offer FHC as a new target in opioid-induced neuropathology.

The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders

Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.

Nuclear pore complex: biochemistry and biophysics of nucleocytoplasmic transport in health and disease

Nuclear pore complexes (NPCs) are the gateways connecting the nucleoplasm and cytoplasm. This structures are composed of over 30 different proteins and 60-125 MDa of mass depending on type of species. NPCs are bilateral pathways that selectively control the passage of macromolecules into and out of the nucleus. Molecules smaller than 40 kDa diffuse through the NPC passively while larger molecules require facilitated transport provided by their attachment to karyopherins. Kinetic studies have shown that approximately 1000 translocations occur per second per NPC. Maintaining its high selectivity while allowing for rapid translocation makes the NPC an efficient chemical nanomachine. In this review, we approach the NPC function via a structural viewpoint. Putting together different pieces of this puzzle, this chapter confers an overall insight into what molecular processes are engaged in import/export of active cargos across the NPC and how different transporters regulate nucleocytoplasmic transport. In the end, the correlation of several diseases and disorders with the NPC structural defects and dysfunctions is discussed.