SLC4A2 Deficiency Causes a New Type of Osteopetrosis

Osteopetrosis is a group of rare inherited skeletal disorders characterized by a marked increase in bone density due to deficient bone resorption. Pathogenic variants in several genes involved in osteoclast differentiation and/or function have been reported to cause osteopetrosis. Solute carrier family 4 member 2 (SLC4A2, encoding anion exchanger 2) plays an important role in osteoclast differentiation and function by exchange of Cl^- with HCO₃^- . Biallelic Slc4a2 loss-of-function mutations in mice and cattle lead to osteopetrosis with osteoclast deficiency; however, pathogenic SLC4A2 variants in humans have not been reported. In this study, we describe a patient with autosomal recessive osteopetrosis due to biallelic pathogenic variants in SLC4A2. We identified novel compound heterozygous variants in SLC4A2 (NM_003040.4: c.556G>A [p.A186T] and c.1658T>C [p.V553A]) by exome sequencing. The measurement of intracellular Cl^- showed that the variants decrease the anion exchange activity of SLC4A2. The impact of the variants on osteoclast differentiation was assessed by a gene knockout-rescue system using a mouse macrophage cell line, RAW 264.7. The Slc4a2-knockout cells show impaired osteoclastogenesis, which was rescued by the wild-type SLC4A2, but not by the mutant SLC4A2s. Immunofluorescence and pit assay revealed that the mutant SLC4A2s leads to abnormal podosome belt formation with impaired bone absorption. This is the first report on an individual affected by SLC4A2-associated osteopetrosis (osteopetrosis, Ikegawa type). With functional studies, we prove that the variants lead to SLC4A2 dysfunction, which altogether supports the importance of SLC4A2 in human osteoclast differentiation. © 2021 American Society for Bone and Mineral Research (ASBMR).

TNFRSF11A-Associated Dysosteosclerosis: A Report of the Second Case and Characterization of the Phenotypic Spectrum

Dysosteosclerosis (DOS) is a distinct form of sclerosing bone disease characterized by irregular osteosclerosis and platyspondyly. DOS is genetically heterogeneous; however, only five cases with SLC29A3 mutations and a single case with a splice-site mutation of TNFRSF11A have been reported, and TNFRSF11A is also a causal gene for osteopetrosis, autosomal recessive 7 (OP-AR7). Thus, the causal genes of DOS and their genotype-phenotype associations remain unclear. In this study, we examined a Japanese patient with DOS and found a novel variant in TNFRSF11A. The homozygous variant was a G to T transversion at the first nucleotide of exon 9 (c.784G>T). Although the variant was predicted to cause a stop codon mutation (p.E262*), in silico evaluation of the exonic splicing elements followed by RT-PCR for the patient-derived cells showed that it caused aberrant splicing due to the change in the exonic splicing element and produced two types of aberrant transcripts: One caused a premature stop codon (p.E262Vfs*17) leading to nonsense mutation-mediated mRNA decay; the other produced a protein with interstitial deletion (p.E262_Q279del). The effects of the mutation on five splicing isoforms of TNFRSF11A were different from those in OP-AR7, but comparable with those in the first DOS with the TNFRSF11A mutation. Thus, we identified the second case of DOS caused by the TNFRSF11A splice-site mutation and confirmed the novel disease entity. © 2019 American Society for Bone and Mineral Research.

Transcription Factor Drug Targets

Transcription factors represent the point of convergence of multiple signaling pathways within eukaryotic cells. Deregulated transcription factors contribute to the pathogenesis of a plethora of human diseases, ranging from diabetes, inflammatory disorders and cardiovascular disease to many cancers, and thus these proteins hold great therapeutic potential. Direct modulation of transcription factor function by small molecules is no longer regarded a Sisyphean task, as recent work in drug discovery has revealed that transcription factors are amenable to drug inhibition. Here in we summarize, recent advances regarding the significance of transcription factors in human diseases and we discuss emerging pharmacological strategies to modulate transcription factor function. J. Cell. Biochem. 117: 2693-2696, 2016. © 2016 Wiley Periodicals, Inc.

Molecular Aberrance in Papillary Thyroid Microcarcinoma Bearing High Aggressiveness: Identifying a "Tibetan Mastiff Dog" From Puppies

Today the most common differentiated thyroid cancer in many countries is papillary thyroid microcarcinoma (PTMC). Although the majority of PTMCs exhibit an indolent clinical course, a few possess high risk for aggressiveness with tumor invasion, metastasis, and even patient mortality. This imposes significant confusion and often dilemma in the clinical management of PTMC. The present review summarizes the molecular pathogenesis, particularly the major genetic alterations, of PTMC that may have prognostic values in assisting risk stratification of this cancer and identification of the most aggressive cases from the many well-behaving cases. J. Cell. Biochem. 117: 1491-1496, 2016. © 2016 Wiley Periodicals, Inc.

Genetic analysis of BMP4 gene in Chinese Han female population with premature ovarian insufficiency

The bone morphogenetic protein 4 (BMP4) gene is related to development of female reproductive organs in animal models. However, to date, there has been no consensus on the relationship between mutations in BMP4 and premature ovarian insufficiency (POI) in human beings. To analyze variations in BMP4 in Chinese women with POI, we sequenced two coding regions of BMP4 in 99 Han Chinese women with POI after DNA extraction and amplification by polymerase chain reaction (PCR). We found no any mutation in the BMP4 coding regions. Only one SNP rs17563 was detected among women with POI. However, the allele frequency of rs17563 presented no significant differences between POI patients and the international HapMap Project data for CHB and CHD. Our findings suggest that the BMP4 gene may not represent a risk factor in the development of POI among Chinese Han women.

Chondrocyte-specific pathology during skeletal growth and therapeutics in a murine model of pseudoachondroplasia

Mutations in the gene encoding cartilage oligomeric matrix protein (COMP) cause pseudoachondroplasia (PSACH), a severe dwarfing condition. Pain, a significant complication, has generally been attributed to joint abnormalities and erosion and early onset osteoarthritis. Previously, we found that the inflammatory-related transcripts were elevated in growth plate and articular cartilages, indicating that inflammation plays an important role in the chondrocyte disease pathology and may contribute to the overall pain sequelae. Here, we describe the effects of D469-delCOMP expression on the skeleton and growth plate chondrocytes with the aim to define a treatment window and thereby reduce pain. Consistent with the human PSACH phenotype, skeletal development of D469del-COMP mice was normal and similar to controls at birth. By postnatal day 7 (P7), the D469del-COMP skeleton, limbs, skull and snout were reduced and this reduction was progressive during postnatal growth, resulting in a short-limbed dwarfed mouse. Modulation of prenatal and postnatal expression of D469del-COMP showed minimal retention/cell death at P7 with some retention/cell death by P14, suggesting that earlier treatment intervention at the time of PSACH diagnosis may produce optimal results. Important and novel findings were an increase in inflammatory proteins generally starting at P21 and that exercise exacerbates inflammation. These observations suggest that pain in PSACH may be related to an intrinsic inflammatory process that can be treated symptomatically and is not related to early joint erosion. We also show that genetic ablation of CHOP dampens the inflammatory response observed in mice expressing D469del-COMP. Toward identifying potential treatments, drugs known to decrease cellular stress (lithium, phenylbutyric acid, and valproate) were assessed. Interestingly, all diminished the chondrocyte pathology but had untoward outcomes on mouse growth, development, and longevity. Collectively, these results define an early treatment window in which chondrocytes can be salvaged, thereby potentially increasing skeletal growth and decreasing pain.

KINETICS OF MATING OF FP+ AND FP- STRAINS OF PSEUDOMONAS AERUGINOSA

Loutit, J. S. (University of Otago, Dunedin, N.Z.), and L. E. Pearce. Kinetics of mating of FP(+) and FP(-) strains of Pseudomonas aeruginosa. J. Bacteriol. 90:425-430. 1965.-Recently, we reported the variability of the FP(+) x FP(-) mating in Pseudomonas aeruginosa, and the increase in efficiency when the cells were mated after dilution. The present work shows that when standardized cells were mated after a dilution of 10(-2) for FP(-) and 2 x 10(-3) for FP(+), there was less variability in the system. Investigation of pairing between FP(+) and FP(-) cells, as measured by genetic transfer, revealed that none took place during 24 hr in liquid media in which growth of both parents was possible. Transfer in liquid minimal medium was not investigated, because the single marker in the male was insufficient to control back mutation in 24 hr. No transfer occurred on solid media which allowed full growth of both FP(+) and FP(-) cells. Transfer took place very slowly on minimal agar, requiring 19 to 20 hr. It is thought that this represents growth of microcolonies with eventual transfer when internal nutrients were exhausted.

UNSTABLE GENETIC TRANSFORMATION IN BACILLUS SUBTILIS AND THE MODE OF INHERITANCE IN UNSTABLE CLONES

Iyer, V. N. (Canada Department of Agriculture, Ottawa, Ont., Canada). Unstable genetic transformation in Bacillus subtilis and the mode of inheritance in unstable clones. J. Bacteriol. 90:495-503. 1965.-An ultraviolet-induced mutant has been isolated from the double auxotroph of Bacillus subtilis (bearing the linked mutations try(2) and his(2)). This mutant has the property of yielding unstable transformants which, in the case of transformation to prototrophy, can be recognized by reduced colony size on minimal agar. Unstable transformant clones usually become stabilized early during the development of the clone (within 12 generations). Analyses of genotypes emerging from such clones on stabilization indicate that in some of these clones the exogenote is transmitted linearly; its integrity is sufficiently preserved that it can participate in two independent recombination events in two different cells. Genetic markers on the exogenote are expressed in situations where genetic integration has not occurred.

TEMPERATURE-SENSITIVE MUTANTS OF BACILLUS SUBTILIS BACTERIOPHAGE SP3. II. IN VIVO COMPLEMENTATION STUDIES

Nishihara, Mutsuko (University of California, Los Angeles), and W. R. Romig. Temperature-sensitive mutants of Bacillus subtilis bacteriophage SP3. II. In vivo complementation studies. J. Bacteriol. 88:1230-1239. 1964.-A plate-spotting procedure was used in initial attempts to group the temperature-sensitive Bacillus subtilis phage SP3 mutants by complementation. The results obtained did not show any clear patterns of reactions among the mutants. Crosses were, therefore, repeated in broth at a temperature of 49 C, which greatly reduced the extent of replication of each mutant type alone. The data on mixed infections indicated that there was a minimum of six complementation groups. Of the 12 isolates, 7 did not seem to complement with each other; the rest complemented with each other and with the seven noncomplementing mutants. There was a positive correlation between the complementation reaction of a pair and the recovery of wild-phenotype phages from a 49 C broth lysate. The relative proportion of phages capable of forming wild-phenotype plaques on plates incubated at 46 C to the total number of plaque-forming units was higher in a lysate of a mixed infection with two mutants than in lysates of each mutant alone. Moreover, this frequency was higher for a mixed lysate made at 49 C than for a lysate of the same two mutants made at 37 C. These observations suggested that genetic recombination might occur at 49 C, and that the increased recovery of wild-phenotype phages in lysates made at this temperature might be due to a selective advantage for these phages. Recombination experiments at 37 C with some complementing pairs gave frequencies of 2.0 to 4.8%. The ratio of wild-phenotype revertants to total phages in the stock lysates used for these crosses at 37 C was less than 10(-6). The noncomplementing mutants were not conclusively shown to be nonidentical.

MUTAGENICITY OF A MONOFUNCTIONAL ALKYLATING AGENT DERIVATIVE OF ACRIDINE IN NEUROSPORA

Purple adenine (ad-3) mutants induced in Neurospora crassa by 2-methoxy-6-chloro-9-(3-[ethyl-2-chloroethyl] aminopropylamino) acridine dihydrochloride (ICR-170) result from intragenic alterations. They are further characterized by low frequencies of leakiness, allelic complementation, and nonpolarized complementation patterns. These characteristics distinguish them from ad-3 mutants induced by x-rays, nitrous acid, and 2-aminopurine.

MUTANT MICE (QUAKING AND JIMPY) WITH DEFICIENT MYELINATION IN THE CENTRAL NERVOUS SYSTEM

Two mutant mice with deficient myelination are described. Quaking is a new autosomal recessive mutant mouse with marked tremor of the hindquarters. The mice eat, swim, breed, and nurse well even though the entire central nervous system is very deficient in myelin by histological and chemical criteria. Myelin formation is impaired; no destruction is seen. Peripheral nerves are myelinated. Jimpy, a known sex-linked mutation, has similar but more severe symptoms and similar pathology, with the additional feature of sudanophilic (nonpolar) lipid distributed in some white-matter tracts. Both mutants offer new opportunities for study of the formation and functions of myelin.

MUTANT GENES REGULATING THE INDUCIBILITY OF KYNURENINE SYNTHESIS

Alterations in the cellular synthesis of kynurenine in the larval fatbody of Drosophila melanogaster may be obtained by feeding the precursor tryptophan or by changing the genotype. In the wild type Ore-R strain, autofluorescent kynurenine globules normally occur in the cells in the anterior regions of the fatbody designated as regions 1, 2, and 3. When tryptophan is included in the larval diet, kynurenine will develop throughout the entire fatbody, thus extending to the cells in regions 4, 5, and 6. In the fatbodies of both the sepia mutant strain and the mutant combinations of the suppressible vermilion alleles with the suppressor gene (su²-s, v¹ and su²-s, v²), kynurenine is found in the cells from region 1 through region 4. This involvement of additional cells in the synthesis of kynurenine occurs under the usual culture conditions for Drosophila. When sepia larvae are fed tryptophan, kynurenine appears in all of the cells of the fatbody. However, dietary tryptophan does not induce kynurenine production in cells in regions 5 and 6 in the mutant combination su²-s, v¹ or su²-s, v². In the latter strains, an increase in the quantity of kynurenine in the fatbody is detected, but this increase remains limited to the same cells in which kynurenine production is found under normal feeding conditions. When the v^36f allele is combined with the su²-s allele, an extremely faint autofluorescence characteristic of kynurenine is found in some of the anteriormost fat cells of regions 1 and 2. This autofluorescence becomes intensified when tryptophan is fed to su²-s, v^36f larvae. The genetic control of kynurenine synthesis in the cells of the fatbody of Drosophila melanogaster has been previously demonstrated. The present observations establish genetic regulation of the ability to induce kynurenine production within a cell through the administration of the inducer tryptophan. Kynurenine production has been considered as a unit function of the cell as a whole rather than of the enzyme alone, and it has been concluded that even though cells in different parts of the body perform this same function (kynurenine production), the gene loci regulating this function may be different for cells in different regions of the body. A phenomenon of overlapping domains of gene actions at the cellular level offers a genetic and cellular basis for developmental and physiological homeostasis.

GENETIC LINKAGE OF MUTATIONAL SITES AFFECTING SIMILAR CHARACTERS IN PNEUMOCOCCUS AND STREPTOCOCCUS

Ravin, Arnold W. (University of Rochester, Rochester, N.Y.), and Joscelyn D. H. De Sa. Genetic linkage of mutational sites affecting similar characters in pneumococcus and streptococcus. J. Bacteriol. 87:86-96. 1964.-By interspecific transformation, deoxyribonucleic acid (DNA) determinants conferring resistance to high levels of streptomycin in pneumococcus were found to be allelic with DNA determinants conferring low levels of streptomycin resistance in the Challis and NBSI strains of streptococcus. The reciprocal transformation (low resistance pneumococcus x high resistance streptococcus) led to the same conclusion. In addition, determinants controlling resistance to erythromycin in pneumococcus and the Challis strain of streptococcus were found to become closely linked after interspecific transformation. Modifier genes influencing the phenotype conferred by mutations at the streptomycin-resistance locus differentiate species to a certain extent. The results demonstrate that transformations between pneumococcus and streptococcus are not due to episomes, but involve recombinational events in which genetic material of the host species is replaced by homologous material that performed a similar function in the donor species.

CULTURE OF DISSOCIATED DROSOPHILA EMBRYOS: AGGREGATED CELLS DIFFERENTIATE AND SORT OUT

When the cells of Drosophila embryos are dissociated and cultured in vitro, aggregation of the cells begins rapidly and movements of the cells continue for at least 5 days. Oenocytes, hypoderm, nerve, muscle, and trachea cells take up characteristic positions in the aggregates. Cells from X2 mutant embryos sort out in identically the same way as do cells from normal embryos.

NEUROSPORA MUTANT LACKING AN ARGININE-SPECIFIC CARBAMYL PHOSPHOKINASE

An arginine-requiring mutant of Neurospora lacks the carbamyl phosphokinase activity present in other strains. Although carbamyl phosphate, the product of this enzyme, is required in both arginine and pyrimidine synthesis, the enzymne appears to serve only the arginine pathway. A pyrimidine specific mode of carbamyl phosphate synthesis is inferred, although it has not yet been demonstrated.

MUTATIONS TO PENICILLIN RESISTANCE IN THE ENTEROBACTERIACEAE THAT AFFECT SENSITIVITY TO SERUM AND VIRULENCE FOR THE MOUSE

Roantree, Robert J. (Stanford University School of Medicine, Stanford, Calif.), and John P. Steward. Mutations to penicillin resistance in the Enterobacteriaceae that affect sensitivity to serum and virulence for the mouse. J. Bacteriol 89:630-639. 1965.-Series of mutants resistant to benzylpenicillin or alpha-aminobenzylpenicillin were derived from serum-resistant strains of Escherichia coli and Salmonella by the gradientplate technique. Serum-sensitive mutants were detected in series derived from 16 of the 19 strains used, and these retained the parental O type. Most series were characterized by a mutational step to a high degree of sensitivity to serum. Penicillin-resistant mutants of virulent S. typhimurium and S. enteritidis were less virulent than the parent strains; those which were very sensitive to serum usually showed the greatest loss of virulence. One class of mutants from S. enteritidis was sensitive to human serum but virulent for mice. We found that the mice lack bactericidal antibody against this strain and that immunization with it leads to a high degree of protection.

COXSACKIE A9 VIRUS: MUTATION FROM DRUG DEPENDENCE TO DRUG INDEPENDENCE

During the multiplication of Coxsackie A9 virus dependent on 2 - (alpha - hydroxybenzyl) - benzimidazole there arise some drug-independent virus particles, which are either drug-resistant or drug-sensitive. We studied the properties of such revertant particles under conditions which did not favor the selection of resistant over sensitive virus particles. These particles exhibited a wide range of responses to 2-(alpha-hydroxybenzyl)-benzimidazole, from high sensitivity to high resistance. Subclones showed the same degree of sensitivity or resistance as the respective parent clones.

REGULATORY MECHANISMS IN THE BIOSYNTHESIS OF ISOLEUCINE AND VALINE. II. IDENTIFICATION OF TWO OPERATOR GENES

Ramakrishnan, T. (Yale University, New Haven, Conn.), and Edward A. Adelberg. Regulatory mechanisms in the biosynthesis of isoleucine and valine. II. Identification of two operator genes. J. Bacteriol. 89:654-660. 1965.-A tightly clustered set of five structural genes governs the synthesis of the five enzymes of isoleucine and valine biosynthesis in Escherichia coli. Three of the genes governing transaminase B, dehydrase, and threonine deaminase, are controlled by a single operator locus, designated oprA. The structural gene governing the condensing enzyme is controlled by a second operator locus, designated oprB. Both oprA and oprB have been shown to regulate structural genes which are cis, but not trans, to their own operator. No mutations have yet been found which affect the level of reductoisomerase, but the existence of a third operator controlling the synthesis of this enzyme can be inferred. Enzyme derepression resulting from mutations in oprA confers resistance to high levels of valine. Derepression of the condensing enzyme resulting from mutations in oprB confers resistance to low levels of valine, and to alpha-aminobutyric acid. The significance of these findings with respect to the valine sensitivity of E. coli strain K-12 is discussed.

USE OF S-METHYLCYSTINE AND CYSTATHIONINE BY METHIONINELESS NEUROSPORA MUTANTS

Wiebers, Joyce L. (Purdue University, West Lafayette, Ind.), and Harold R. Garner. Use of S-methylcysteine and cystathionine by methionineless Neurospora mutants. J. Bacteriol. 88:1798-1804. 1964.-Radioactive methionine was found in hydrolysates of various strains of Neurospora crassa when either S-methylcysteine (SMC)-C(14)H(3) or SMC-S(35) is the sole addition to minimal medium. Isotope product-precursor specific activity ratios are very similar for the two sources of label. Wild-type and methionineless mutants use sulfur from SMC in the biosynthesis of methionine, but not of cysteine, when grown in regular medium. With a medium nearly free from sulfate, SMC served as a source of sulfur for both cysteine and methionine. Suppressed methionineless mutants incorporated sulfur from SMC into cellular cysteine even in the presence of normal amounts of sulfate. SMC as a possible metabolic precursor of methionine was compared to cystathionine in an experiment with wild-type Neurospora. The four sources of label used were: SMC-C(14)H(3), SMC-S(35), cystathionine-U-C(14), and cystathionine-S(35). In each flask, the organism was offered one of the labeled compounds plus an equivalent amount of the other compound without label. The amount of each compound was sufficient for either to supply its contribution to all of the cellular methionine, if it were successful in competing with endogenous sources. To avoid adaptive breakdown of substrates, the compounds were added continuously at a rate consistent with the amount of growth present. The ratio of specific activity of cellular methionine to precursor was determined for each labeled compound. The results show that SMC sulfur and methyl carbon are used equally well. Cystathionine carbon and sulfur appear to be equally utilized also. A preference for cystathionine is indicated.