Sall4 regulates posterior trunk mesoderm development by promoting mesodermal gene expression and repressing neural genes in the mesoderm

The trunk axial skeleton develops from paraxial mesoderm cells. Our recent study demonstrated that conditional knockout of the stem cell factor Sall4 in mice by TCre caused tail truncation and a disorganized axial skeleton posterior to the lumbar level. Based on this phenotype, we hypothesized that, in addition to the previously reported role of Sall4 in neuromesodermal progenitors, Sall4 is involved in the development of the paraxial mesoderm tissue. Analysis of gene expression and SALL4 binding suggests that Sall4 directly or indirectly regulates genes involved in presomitic mesoderm differentiation, somite formation and somite differentiation. Furthermore, ATAC-seq in TCre; Sall4 mutant posterior trunk mesoderm shows that Sall4 knockout reduces chromatin accessibility. We found that Sall4-dependent open chromatin status drives activation and repression of WNT signaling activators and repressors, respectively, to promote WNT signaling. Moreover, footprinting analysis of ATAC-seq data suggests that Sall4-dependent chromatin accessibility facilitates CTCF binding, which contributes to the repression of neural genes within the mesoderm. This study unveils multiple mechanisms by which Sall4 regulates paraxial mesoderm development by directing activation of mesodermal genes and repression of neural genes.

Sall genes regulate hindlimb initiation in mouse embryos

Vertebrate limbs start to develop as paired protrusions from the lateral plate mesoderm at specific locations of the body with forelimb buds developing anteriorly and hindlimb buds posteriorly. During the initiation process, limb progenitor cells maintain active proliferation to form protrusions and start to express Fgf10, which trigger molecular processes for outgrowth and patterning. Although both processes occur in both types of limbs, forelimbs (Tbx5) and hindlimbs (Isl1) utilize distinct transcriptional systems to trigger their development. Here, we report that Sall1 and Sall4, zinc finger transcription factor genes, regulate hindlimb initiation in mouse embryos. Compared to the 100% frequency loss of hindlimb buds in TCre; Isl1 conditional knockouts, Hoxb6Cre; Isl1 conditional knockout causes a hypomorphic phenotype with only approximately 5% of mutants lacking the hindlimb. Our previous study of SALL4 ChIP-seq showed SALL4 enrichment in an Isl1 enhancer, suggesting that SALL4 acts upstream of Isl1. Removing one allele Sall4 from the hypomorphic Hoxb6Cre; Isl1 mutant background caused loss of hindlimbs, but removing both alleles caused an even higher frequency of loss of hindlimbs, suggesting a genetic interaction between Sall4 and Isl1. Furthermore, TCre-mediated conditional double knockouts of Sall1 and Sall4 displayed a loss of expression of hindlimb progenitor markers (Isl1, Pitx1, Tbx4) and failed to develop hindlimbs, demonstrating functional redundancy between Sall1 and Sall4. Our data provides genetic evidence that Sall1 and Sall4 act as master regulators of hindlimb initiation.

[Effects and mechanisms of bariatric surgery on sexual function in males with obesity]

Obesity has been identified as one of the risk factors for male sexual dysfunction, and it also has a certain impact on fertility. For people with obesity, sexual function is an important aspect of quality of life, but it is often overlooked. Society's stigma against obesity exacerbates the psychological stress of patients with obesity and negatively affects sexual function. Current studies have found that bariatric surgery can reduce body weight and improve sexual function in patients with obesity, and obesity-related gonadal dysfunction is also improved or even subsided after surgery. However, attention needs to be paid to postoperative body mass management and mental health status of patients to prevent postoperative body mass recovery and reversal of sex hormones and sexual function. In addition, there is still controversy about the change in sperm quality after bariatric surgery, and there is a lack of research data on sexual function and sperm parameters and mechanisms after bariatric surgery. Therefore, this article reviews the latest research progress of bariatric surgery and sexual dysfunction, as well as related mechanisms and sperm parameters, to provide a reference for bariatric surgery in patients with obesity with sexual dysfunction.

Sall4 restricts glycolytic metabolism in limb buds through transcriptional regulation of glycolytic enzyme genes

Recent studies illustrate the importance of regulation of cellular metabolism, especially glycolysis and pathways branching from glycolysis, during vertebrate embryo development. For example, glycolysis generates cellular energy ATP. Glucose carbons are also directed to the pentose phosphate pathway, which is needed to sustain anabolic processes in the rapidly growing embryos. However, our understanding of the exact status of glycolytic metabolism as well as genes that regulate glycolytic metabolism are still incomplete. Sall4 is a zinc finger transcription factor that is highly expressed in undifferentiated cells in developing mouse embryos, such as blastocysts and the post-implantation epiblast. TCre; Sall4 conditional knockout mouse embryos exhibit various defects in the posterior part of the body, including hindlimbs. Using transcriptomics approaches, we found that many genes encoding glycolytic enzymes are upregulated in the posterior trunk, including the hindlimb-forming region, of Sall4 conditional knockout mouse embryos. In situ hybridization and qRT-PCR also confirmed upregulation of expression of several glycolytic genes in hindlimb buds. A fraction of those genes are bound by SALL4 at the promoters, gene bodies or distantly-located regions, suggesting that Sall4 directly regulates expression of several glycolytic enzyme genes in hindlimb buds. To further gain insight into the metabolic status associated with the observed changes at the transcriptional level, we performed a comprehensive analysis of metabolite levels in limb buds in wild type and Sall4 conditional knockout embryos by high-resolution mass spectrometry. We found that the levels of metabolic intermediates of glycolysis are lower, but glycolytic end-products pyruvate and lactate did not exhibit differences in Sall4 conditional knockout hindlimb buds. The increased expression of glycolytic genes would have caused accelerated glycolytic flow, resulting in low levels of intermediates. This condition may have prevented intermediates from being re-directed to other pathways, such as the pentose phosphate pathway. Indeed, the change in glycolytic metabolite levels is associated with reduced levels of ATP and metabolites of the pentose phosphate pathway. To further test whether glycolysis regulates limb patterning downstream of Sall4, we conditionally inactivated Hk2, which encodes a rate-limiting enzyme gene in glycolysis and is regulated by Sall4. The TCre; Hk2 conditional knockout hindlimb exhibited a short femur, and a lack of tibia and anterior digits in hindlimbs, which are defects similarly found in the TCre; Sall4 conditional knockout. The similarity of skeletal defects in Sall4 mutants and Hk2 mutants suggests that regulation of glycolysis plays a role in hindlimb patterning. These data suggest that Sall4 restricts glycolysis in limb buds and contributes to patterning and regulation of glucose carbon flow during development of limb buds.

Etv2 regulates enhancer chromatin status to initiate Shh expression in the limb bud

Sonic hedgehog (Shh) is essential for limb development, and the mechanisms that govern the propagation and maintenance of its expression has been well studied; however, the mechanisms that govern the initiation of Shh expression are incomplete. Here we report that ETV2 initiates Shh expression by changing the chromatin status of the developmental limb enhancer, ZRS. Etv2 expression precedes Shh in limb buds, and Etv2 inactivation prevents the opening of limb chromatin, including the ZRS, resulting in an absence of Shh expression. Etv2 overexpression in limb buds causes nucleosomal displacement at the ZRS, ectopic Shh expression, and polydactyly. Areas of nucleosome displacement coincide with ETS binding site clusters. ETV2 also functions as a transcriptional activator of ZRS and is antagonized by ETV4/5 repressors. Known human polydactyl mutations introduce novel ETV2 binding sites in the ZRS, suggesting that ETV2 dosage regulates ZRS activation. These studies identify ETV2 as a pioneer transcription factor (TF) regulating the onset of Shh expression, having both a chromatin regulatory role and a transcriptional activation role.

The embryonic limb bud is known to be patterned by a Shh morphogen gradient, though how Shh expression is activated remains less clear. Here the authors show that Etv2 acts as a pioneer transcription factor to mediate accessibility of the ZRS enhancer and initiate Shh expression.

Development of the Proximal-Anterior Skeletal Elements in the Mouse Hindlimb Is Regulated by a Transcriptional and Signaling Network Controlled by Sall4

The vertebrate limb serves as an experimental paradigm to study mechanisms that regulate development of the stereotypical skeletal elements. In this study, we simultaneously inactivated Sall4 using Hoxb6Cre and Plzf in mouse embryos, and found that their combined function regulates development of the proximal-anterior skeletal elements in hindlimbs. The Sall4; Plzf double knockout exhibits severe defects in the femur, tibia, and anterior digits, distinct defects compared to other allelic series of Sall4; Plzf We found that Sall4 regulates Plzf expression prior to hindlimb outgrowth. Further expression analysis indicated that Hox10 genes and GLI3 are severely downregulated in the Sall4; Plzf double knockout hindlimb bud. In contrast, PLZF expression is reduced but detectable in Sall4; Gli3 double knockout limb buds, and SALL4 is expressed in the Plzf; Gli3 double knockout limb buds. These results indicate that Plzf, Gli3, and Hox10 genes downstream of Sall4, regulate femur and tibia development. In the autopod, we show that Sall4 negatively regulates Hedgehog signaling, which allows for development of the most anterior digit. Collectively, our study illustrates genetic systems that regulate development of the proximal-anterior skeletal elements in hindlimbs.

Sall4 regulates neuromesodermal progenitors and their descendants during body elongation in mouse embryos

Bi-potential neuromesodermal progenitors (NMPs) produce both neural and paraxial mesodermal progenitors in the trunk and tail during vertebrate body elongation. We show that Sall4, a pluripotency-related transcription factor gene, has multiple roles in regulating NMPs and their descendants in post-gastrulation mouse embryos. Sall4 deletion using TCre caused body/tail truncation, reminiscent of early depletion of NMPs, suggesting a role of Sall4 in NMP maintenance. This phenotype became significant at the time of the trunk-to-tail transition, suggesting that Sall4 maintenance of NMPs enables tail formation. Sall4 mutants exhibit expanded neural and reduced mesodermal tissues, indicating a role of Sall4 in NMP differentiation balance. Mechanistically, we show that Sall4 promotion of WNT/β-catenin signaling contributes to NMP maintenance and differentiation balance. RNA-Seq and SALL4 ChIP-Seq analyses support the notion that Sall4 regulates both mesodermal and neural development. Furthermore, in the mesodermal compartment, genes regulating presomitic mesoderm differentiation are downregulated in Sall4 mutants. In the neural compartment, we show that differentiation of NMPs towards post-mitotic neuron is accelerated in Sall4 mutants. Our results collectively provide evidence supporting the role of Sall4 in regulating NMPs and their descendants.

[Differentiation and malignant suppression induced by mouse erythroid differentiation and denucleation factor on mouse erythroleukemia cells]

OBJECTIVE

To investigate the roles of mouse erythroid differentiation and denucleation factor (MEDDF), newly cloned in our laboratory, in erythroid terminal differentiation.

METHODS

Mouse erythroleukemia cells (MEL) were transfected with eukaryotic expression plasmid pcDNA-MEDDF. The changes of cell growth rate, mitotic index and colony-forming rate in semi-solid medium were investigated. The expressions of c-myc and beta-globin genes were analysed by semi-quantitative RT-PCR.

RESULTS

MEL cells transfected with pcDNA-MEDDF showed significant lower growth rate, mitotic index, and colony-forming rate in semisolid medium(P < 0.01). The percentage of benzidine-positive cells was 32.8% after transfection. The expression of beta-globin in cells transfected with pcDNA-MEDDF was 3.43 times higher than that of control (MEL transfected with blank vector, pcDNA3.1), and the expression of c-myc was decreased by 66.3%.

CONCLUSIONS

MEDDF can induce differentiation of MEL cell, and suppress its malignancy likely.

Effect of topical aclacinomycin on glaucoma filtration surgery in rabbits

A prospective, randomized, double-masked and placebo-controlled study was performed to compare the effects of a single 5-minute intraoperative exposure to aclacinomycin (AMC) 0.4 mg/ml or 0.8 mg/ml with control eyes treated with saline solution on the success of glaucoma filtration surgery in 26 rabbits. Intraocular pressure (IOP), bleb survival, fistula patency and complications were evaluated. The results showed that IOP in the eyes treated with AMC was significantly lower than that in the control eyes from days 5-40 in the 0.4 mg/ml group and from days 5-20 in the 0.8 mg/ml group. The bleb survival lasted significantly longer in the two treated groups than in the control group and in the AMC 0.4 mg/ml group than in the AMC 0.8 mg/ml group. At 40 days, the rate of sclera fistula occlusion was 0% in the AMC 0.4 mg/ml eyes, 43.8% in the AMC 0.8 mg/ml eyes, and 100% in the control eyes. Significant complications, such as anterior chamber inflammation, hyphema, moderate and severe corneal haze, dense corneal neovascularization and mild cataract occurred only in the eyes treated with AMC 0.8 mg/ml. The results indicated that intraocular treatment with AMC at a dose of 0.4 mg/ml had a markedly beneficial effect on IOP, bleb appearance and fistula patency after experimental filtration surgery in rabbits.

Effect of subconjunctival daunorubicin on glaucoma surgery in rabbits

Daunorubicin (DNR), an antibiotic-antimetabolite, was used as an adjunct to standardized partial-thickness filtration surgery in 21 rabbits to determine its effects on that surgery. Postoperatively, one of the eyes of each rabbit received subconjunctival injections of DNR 25 micrograms or 50 micrograms, while the fellow eyes received only diluent, daily for 2 to 14 days. Bleb survival, fistula patency, the thickness of the subconjunctival connective tissue, and postoperative complications were investigated. The filtration blebs lasted significantly longer (P < .005), the rate of fistula closure was significantly lower (P < .005), and the subepithelial connective tissue was much looser and thicker in the experimental eyes than in the control eyes. Corneal toxicity occurred more frequently in the eyes treated with the higher-dose DNR than in those treated with the lower dose and in the control eyes.

Enzyme engineering for nonaqueous solvents: random mutagenesis to enhance activity of subtilisin E in polar organic media

Enzyme activity is often dramatically reduced in polar organic solvents, even under conditions where the folded structures are stable. We have utilized random mutagenesis by polymerase chain reaction (PCR) techniques combined with screening for enhanced activity in the presence of dimethylformamide (DMF) to probe mechanisms by which improved enzymes for chemical synthesis in polar organic media might be obtained. Two amino acid substitutions which enhance subtilisin E activity in the presence of DMF, Q103R and D60N, were identified by screening on agar plates containing DMF and casein. The two substitutions are located near the substrate binding pocket or in the active site, and their effects on the catalytic efficiency kcat/KM for the hydrolysis of a peptide substrate are additive. The effects of D60N are apparent only in the presence of DMF, highlighting the importance of screening in the organic solvent. Protein engineering is an effective approach to enhancing enzyme activity in organic media: the triple mutant D60N + Q103R + N218S is 38 times more active than wild-type subtilisin E in 85% DMF. An evolutionary approach consisting of multiple steps of random mutagenesis and screening in continually higher concentrations of organic solvent should result in enzymes that are substantially more active in organic media.

Characterization of the structure and transcription of an ubiquitin fusion gene from maize

We have identified a maize ubiquitin (Ubi) fusion gene (UBF9) by screening a maize W22 genomic phage lambda library with a short (16-nucleotide) oligodeoxyribonucleotide probe derived from the sequence for the extension sequence of a yeast UB13 fusion gene. UBF9 consists of an UB monomer sequence (228 bp long) joined to an extension sequence (237 bp long). The extension sequence encodes a protein of 79 amino acids which shares extensive identity with similar extension aa sequences found in yeast, humans, barley and Arabidopsis thaliana. UBF9 encodes a small-size class of Ubi mRNAs in the maize tissues investigated. The UBF9 transcript is present in high levels in maize endosperm tissues 22 days after pollination. Genomic Southern blots of maize inbred W22 DNA indicate that the fusion gene sequences are present in multiple copies in the maize genome. Primer extension experiments indicate that the transcription start point is located at 80 bp upstream from the translation start codon of UBF9. Two 37-bp tandem repeated A + T-rich sequences are found in the 5'-flanking region of UBF9. The A + T-rich sequences share the motif, AATATTTTATT, which is present in a diverse set of plant genes.

Enzyme engineering for nonaqueous solvents. II. Additive effects of mutations on the stability and activity of subtilisin E in polar organic media

Single amino acid substitutions increase the activity and stability of subtilisin E in mixtures of organic solvents and water, and the effects of these mutations are additive. A variant of subtilisin E that exhibits higher activity in mixtures of dimethylformamide (DMF) and water (Q103R) was created by random mutagenesis combined with screening for improved activity (K. Chen and F. H. Arnold, in preparation). Another mutation, N218S, known to improve both the activity and stability of subtilisin BPN', also improves the activity and stability of subtilisin E in the presence of DMF. The effects of the two substitutions on transition-state stabilization are additive. Furthermore, the Q103R mutation that improves activity has no deleterious effect on subtilisin stability. The double mutant Q103R+N218S is 10 times more active than the wild-type enzyme in 20% (v/v) DMF and twice as stable in 40% DMF. Although the effects of single mutations can be impressive, a practical strategy for engineering enzymes that function in nonaqueous solvents will most likely require multiple changes in the amino acid sequence. These results demonstrate the excellent potential for engineering nonaqueous-solvent-compatible enzymes.

Sites of action of gossypol studied by autoradiography and enzyme histochemistry

The distribution of 14C-gossypol acetate was studied by autoradiography in male rats after intraperitoneal or intratesticular injection. Accumulation of radioactivity was found in testis, kidney and liver, while there was little in brain, pituitary and epididymis. In testis, high accumulation occurred in interstitial cells, with low levels in Sertoli cells, spermatogonia and spermatocytes. In addition, the chronic effect of gossypol was assessed by enzyme histochemistry with thiamine pyrophosphate, alpha-glycerophosphate dehydrogenase, and by lipid stain. In the treated animals an increased number of luminal exfoliated cells (Sertoli cells, germ cells and spermatids) was noted, which showed positive reactions. The results suggest both direct and indirect effects of gossypol on testicular functions.