A thermolabile aldolase A mutant causes fever-induced recurrent rhabdomyolysis without hemolytic anemia

Aldolase A deficiency has been reported as a rare cause of hemolytic anemia occasionally associated with myopathy. We identified a deleterious homozygous mutation in the ALDOA gene in 3 siblings with episodic rhabdomyolysis without hemolytic anemia. Myoglobinuria was always triggered by febrile illnesses. We show that the underlying mechanism involves an exacerbation of aldolase A deficiency at high temperatures that affected myoblasts but not erythrocytes. The aldolase A deficiency was rescued by arginine supplementation in vitro but not by glycerol, betaine or benzylhydantoin, three other known chaperones, suggesting that arginine-mediated rescue operated by a mechanism other than protein chaperoning. Lipid droplets accumulated in patient myoblasts relative to control and this was increased by cytokines, and reduced by dexamethasone. Our results expand the clinical spectrum of aldolase A deficiency to isolated temperature-dependent rhabdomyolysis, and suggest that thermolability may be tissue specific. We also propose a treatment for this severe disease.

Mutations in human lipoyltransferase gene LIPT1 cause a Leigh disease with secondary deficiency for pyruvate and alpha-ketoglutarate dehydrogenase

BACKGROUND

Synthesis and apoenzyme attachment of lipoic acid have emerged as a new complex metabolic pathway. Mutations in several genes involved in the lipoic acid de novo pathway have recently been described (i.e., LIAS, NFU1, BOLA3, IBA57), but no mutation was found so far in genes involved in the specific process of attachment of lipoic acid to apoenzymes pyruvate dehydrogenase (PDHc), α-ketoglutarate dehydrogenase (α-KGDHc) and branched chain α-keto acid dehydrogenase (BCKDHc) complexes.

METHODS

Exome capture was performed in a boy who developed Leigh disease following a gastroenteritis and had combined PDH and α-KGDH deficiency with a unique amino acid profile that partly ressembled E3 subunit (dihydrolipoamide dehydrogenase / DLD) deficiency. Functional studies on patient fibroblasts were performed. Lipoic acid administration was tested on the LIPT1 ortholog lip3 deletion strain yeast and on patient fibroblasts.

RESULTS

Exome sequencing identified two heterozygous mutations (c.875C > G and c.535A > G) in the LIPT1 gene that encodes a mitochondrial lipoyltransferase which is thought to catalyze the attachment of lipoic acid on PDHc, α-KGDHc, and BCKDHc. Anti-lipoic acid antibodies revealed absent expression of PDH E2, BCKDH E2 and α-KGDH E2 subunits. Accordingly, the production of 14CO2 by patient fibroblasts after incubation with 14Cglucose, 14Cbutyrate or 14C3OHbutyrate was very low compared to controls. cDNA transfection experiments on patient fibroblasts rescued PDH and α-KGDH activities and normalized the levels of pyruvate and 3OHbutyrate in cell supernatants. The yeast lip3 deletion strain showed improved growth on ethanol medium after lipoic acid supplementation and incubation of the patient fibroblasts with lipoic acid decreased lactate level in cell supernatants.

CONCLUSION

We report here a putative case of impaired free or H protein-derived lipoic acid attachment due to LIPT1 mutations as a cause of PDH and α-KGDH deficiencies. Our study calls for renewed efforts to understand the mechanisms of pathology of lipoic acid-related defects and their heterogeneous biochemical expression, in order to devise efficient diagnostic procedures and possible therapies.

Functional and electrophysiological characterization of four non-truncating mutations responsible for creatine transporter (SLC6A8) deficiency syndrome

Intellectual disability coupled with epilepsy are clinical hallmarks of the creatine (Cr) transporter deficiency syndrome resulting from mutations in the SLC6A8 gene. So far characterization of pathogenic mutations of SLC6A8 has been limited to Cr uptake. The aim of our study was to characterize the electrogenic and pharmacological properties of non truncating SLC6A8 mutations identified in patients presenting variable clinical severity. Electrophysiological and pharmacological properties of four mutants (including two novel ones) were studied in X. laevis oocyte expression system. Creatine uptake was assessed with [(14)C]-Cr in X. laevis and patients' fibroblasts. Subcellular localization was determined by immunofluorescence and western blot. All mutants were properly targeted to the plasma membrane in both systems. Mutations led to the complete loss of both electrogenic and transport activities in X. laevis and Cr uptake in patients' fibroblasts. Among the Cr analogs tested, guanidinopropionate induced an electrogenic activity with the normal SLC6A8 transporter similar to creatine whereas a phosphocreatine derivative, PCr-Mg-CPLX, resulted in partial activity. SLC6A8 mutants displayed no electrogenic activity with all Cr analogs tested in X. laevis oocytes. Although the mutations altered various domains of SLC6A8 Cr uptake and electrogenic properties were completely inhibited and could not be dissociated. Besides the metabolic functions of Cr, the loss of SLC6A8 electrogenic activity, demonstrated here for the first time, may also play a role in the altered brain functions of the patients.

Hereditary hyperferritinemia cataract syndrome: clinical, genetic, and laboratory findings in 5 families

BACKGROUND

The hereditary hyperferritinemia cataract syndrome (HHCS) is an autosomal dominant disorder characterized by high serum ferritin and early onset cataract. Mutations in the iron responsive element (IRE) within the 5' untranslated region of the L-ferritin (FTL) gene lead to constitutive L-ferritin synthesis resulting in hyperferritinemia. Bilateral cataract formation is caused by the intracellular accumulation of ferritin in the lens.

PATIENTS

4 children from unrelated families were referred for further exploration of hyperferritinemia which was detected during the diagnostic work-up of gastroenterological or hematological disorders. 1 patient was primarily referred for the investigation of bilateral cataract.Diagnostics included routine blood analysis, including complete blood count, iron status, liver and kidney parameters, a physical and an ophthalmological examination. Molecular genetic analysis of the FTL IRE was performed in 4 patients by PCR from genomic DNA and subsequent direct sequencing.

RESULTS

All index patients presented with isolated hyperferritinemia without iron overload and had a positive family history for early onset cataract. Age at onset and disease severity varied between different families and among family members. Molecular genetic analysis revealed point mutations within the FTL IRE.

CONCLUSION

In patients with hyperferritinemia but without any other sign of iron overload or inflammation HHCS should be considered to avoid complex and invasive procedures. Vice versa, in patients with familial inherited cataract the early serum ferritin measurement helps to avoid unnecessary diagnostics.

Parathyroid adenomectomy under local anesthesia with intra-operative monitoring of UcAMP and/or 1-84 PTH

Because 80% of patients with primary hyperparathyroidism have a single adenoma and because most adenomas are now visualized by ultrasonography, we have attempted to remove these suspected single adenomas under local anesthesia with intra-operative monitoring of urinary cAMP (UcAMP) and 1-84 parathyroid hormone (PTH) serum levels. In the last 2 years, 45 patients (mean age 65 years) with primary hyperparathyroidism underwent surgery with local anesthesia when a single adenoma was strongly suspected by ultrasonography. Patients with equivocal or misleading ultrasonography, e.g., those with associated thyroid or multiglandular pathology and those who were non-cooperative, were excluded from this procedure. UcAMP and 1-84 PTH were determined prior to the incision, at the time of removal of the adenoma, and at regular intervals until 120 minutes after the operation. Results were available 45 min to 60 min after sampling for PTH and 60 min to 80 min for UcAMP. Forty-two adenomas were removed through a 2 cm to 3 cm skin incision in a mean time of 25 minutes, with no adverse effect, no morbidity, and minimal discomfort. The 42 patients were normocalcaemic on follow-up. The monitorings always predicted the success of the operation. In the 3 remaining patients, because the monitorings remained elevated at the end of the procedure, the patients underwent classical bilateral neck dissection under general anesthesia. This new approach can be safely accomplished with short operative time and hospital stay. The absence of general anesthesia is reassuring for the patients who are reluctant to undergo general anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

[Excision under local anesthesia of parathyroid adenomas. Criteria of selection and control of effectiveness. 35 cases]

Primary hyperparathyroidism caused by an adenoma that has been identified and localized by ultrasonography can be treated through a limited approach route, under local anaesthesia, provided the effect of excision is controlled by a perioperative assay of urinary cAMP or, preferably, of plasma parathormone level, and provided the contra-indications of this method are respected. Thirty-three out of 35 patients have been successfully operated upon by this method. In case of failure confirmed by laboratory tests, local anaesthesia was only a prelude to cervicotomy under general anaesthesia.

Two statistical approaches to nuclei shape and size in a morphometric description of lymph node sections in non-Hodgkin's lymphoma

An attempt is made to evaluate more clearly the potential contribution of quantitative nuclear profile shape and size measurements to lymph node section histologic description in 70 cases of non-Hodgkin's lymphoma (NHL). The area of nuclear profiles and five nonredundant and size-free shape indices were measured using the THECLA program on a Leitz Texture Analysis System (Leitz-TAS). Two statistical approaches were applied, known respectively as "parametric," (first statistical moments of variable distributions over samples of 200 nuclear profiles) and "nonparametric," which are percentages of nuclear profiles distributed into five "cytological" classes that are defined by shape: round (A), elongated (B), kidney shaped (C), irregular (D) and cleaved (E) nuclear profiles. Both statistical approaches provide proper overall discrimination of the eight histological categories identified with reasonable reliability by pathologists. Above all, the present report discusses the ability of a set of parametric and nonparametric variables to describe NHL cell populations, in an objective and meaningful way, according to nuclei shape. A method of synthesizing multidimensional correlations (CORICO program) is proposed in support of the discussion. Also, the specific descriptive power of each of the variables is described; in particular, it is concluded that there is a close link between the shape and size of the nuclear profiles of the cells.

Prognostic significance of a morphometric study of lymph node biopsies in chronic lymphocytic leukaemia

In 18 chronic lymphocytic leukaemia (CLL) and 2 diffuse, well-differentiated lymphoma (DWDL) lymph node biopsies, morphometric results analysing nuclear area distribution curves by the skewness coefficient were compared to histological findings, clinical stage and survival. Lymphocytic proliferation was subclassified according to the number and the distribution of large lymphoid cells. All cases with a component of large lymphoid cells had a right deviation of the nuclear area distribution curve and a positive value of the skewness coefficient in contrast to those where lymphocytic proliferation was monomorphous. Good correlation was observed between histological findings, morphometric analysis and survival: most patients with a right deviation of nuclear area distribution curve and positive skewness coefficient are clinically stage C, or died within 2-44 months, in contrast to patients with a symmetric distribution of nuclear area curve who are clinically stage A or B and still alive. The results indicate that in CCL and DWDL the lymph node biopsy with quantitative analysis has prognostic significance.

An application of mathematical morphology to analysis of the size and shape of nuclei in tissue sections of non-Hodgkin's lymphoma

Using principles from the theory of mathematical morphology, a semiautomatic analysis of the size and shape of cell nuclei on tissue sections was carried out on a Leitz Texture Analysis System (Leitz-TAS). The four parameters proposed here are more discriminatory than conventional shape evaluation by the form factor (FF), which is based on the ratio of perimeter squared to area. The parameters quantified, respectively, nuclear elongation (ND), narrow (R1) and wide (R2) irregularities, and the distribution of R1 and R2 along the nuclear contour (ID). The properties of these parameters were tested nucleus-by-nucleus on 24 nuclear models. The methodology was then illustrated by a study of lymph node nuclei in non-Hodgkin's lymphoma (NHL). Prior to analysis, 45 lymphomas were classified into five categories of nuclear size and shape according to the International Working Formulation (IWF). Two hundred nuclei were measured on each lymph node section. Statistical interpretation was based upon an analysis of the nuclear surface area on sections and upon the mean values of R1, R2, and ND, the standard deviations of R1 and R2, and the percentage of cleaved nuclei detected by ID. The mean value of R2 discriminated best between the two sets of populations with regular and irregular nuclear contours, respectively. Parameters R1, ND, and ID permitted the distinction of certain NHL cases among populations with irregular nuclei. Nuclear invaginations decreased in depth as the nuclear area became greater. The median surface area was well correlated to the IWF, and the skewness coefficient (third statistical moment of the nuclear surface area distribution) was related to the number of nuclear size or shape subpopulations.

Lymphadenopathy in patients at risk for acquired immunodeficiency syndrome. Histopathology and histochemistry

Lymph node biopsies of 12 patients at high risk for acquired immunodeficiency syndrome (AIDS) with generalized lymphadenopathy (AIDS-related complex [ARC]) and seven controls with conventional lymph node hyperplasia were examined by light microscopy and immunohistochemical staining of frozen tissue. The immunohistochemical results were quantified by planimetric means. Our findings show that the T helper/T suppressor-cytotoxic (Th/Tsc) ratio in lymph nodes from ARC patients is significantly decreased with respect to controls and that this decrease precedes the change in the Th/Tsc ratio in peripheral blood. Our findings distinguish between lymphadenopathy from patients with ARC and other forms of hyperplasia; the relation to AIDS is discussed.