The AUXIN RESPONSE FACTOR (ARF) gene family products, together with the AUXIN/INDOLE-3-ACETIC ACID proteins, regulate auxin-mediated transcriptional activation/repression. The biological function(s) of most ARFs is poorly understood. Here, we report the identification and characterization of T-DNA insertion lines for 18 of the 23 ARF gene family members in Arabidopsis thaliana. Most of the lines fail to show an obvious growth phenotype except of the previously identified arf2/ hss, arf3/ett, arf5/mp, and arf7/nph4 mutants, suggesting that there are functional redundancies among the ARF proteins. Subsequently, we generated double mutants. arf7 arf19 has a strong auxin-related phenotype not observed in the arf7 and arf19 single mutants, including severely impaired lateral root formation and abnormal gravitropism in both hypocotyl and root. Global gene expression analysis revealed that auxin-induced gene expression is severely impaired in the arf7 single and arf7 arf19 double mutants. For example, the expression of several genes, such as those encoding members of LATERAL ORGAN BOUNDARIES domain proteins and AUXIN-REGULATED GENE INVOLVED IN ORGAN SIZE, are disrupted in the double mutant. The data suggest that the ARF7 and ARF19 proteins play essential roles in auxin-mediated plant development by regulating both unique and partially overlapping sets of target genes. These observations provide molecular insight into the unique and overlapping functions of ARF gene family members in Arabidopsis.

START lipid/sterol-binding domains are amplified in plants and are predominantly associated with homeodomain transcription factors

A survey of proteins containing lipid/sterol-binding StAR-related lipid transfer (START) domains shows that they are amplified in plants and are primarily found within homeodomain (HD) transcription factors.

Dominant mutations in the mitochondrial paralogs coiled-helix-coiled-helix (CHCHD) domain 2 (C2) and CHCHD10 (C10) were recently identified as causing Parkinson’s disease and amyotrophic lateral sclerosis/frontotemporal dementia/myopathy, respectively. The mechanism by which they disrupt mitochondrial cristae, however, has been uncertain. Using the first C2/C10 double knockout (DKO) mice, we report that C10 pathogenesis and the normal function of C2/C10 are intimately linked. Similar to patients with C10 mutations, we found that C2/C10 DKO mice have disrupted mitochondrial cristae, because of cleavage of the mitochondrial-shaping protein long form of OPA1 (L-OPA1) by the stress-induced peptidase OMA1. OMA1 was found to be activated similarly in affected tissues of mutant C10 knock-in (KI) mice, demonstrating that L-OPA1 cleavage is a novel mechanism for cristae abnormalities because of both C10 mutation and C2/C10 loss. Using OMA1 activation as a functional assay, we found that C2 and C10 are partially functionally redundant, and some but not all disease-causing mutations have retained activity. Finally, C2/C10 DKO mice partially phenocopied mutant C10 KI mice with the development of cardiomyopathy and activation of the integrated mitochondrial integrated stress response in affected tissues, tying mutant C10 pathogenesis to C2/C10 function.

Mutations in paralogous mitochondrial proteins CHCHD2 and CHCHD10 cause autosomal dominant Parkinson Disease (PD) and Amyotrophic Lateral Sclerosis/Frontotemporal Dementia (ALS/FTD), respectively. Using newly generated CHCHD2, CHCHD10 and CHCHD2/10 double knockout cell lines, we find that the proteins are partially functionally redundant, similarly distributed throughout the mitochondrial cristae, and form heterodimers. Unexpectedly, we also find that CHCHD2/CHCHD10 heterodimerization increases in response to mitochondrial stress. This increase is driven by differences in the proteins' stability and mutual affinity: CHCHD2 is preferentially stabilized by loss of mitochondrial membrane potential, and CHCHD10 oligomerization depends on CHCHD2 expression. Exploiting the dependence of CHCHD10 oligomerization on CHCHD2, we developed a heterodimer incorporation assay and demonstrate that CHCHD2 and CHCHD10 with disease-causing mutations readily form heterodimers. As we also find that both proteins are highly expressed in human Substantia nigra and cortical pyramidal neurons, mutant CHCHD2 and CHCHD10 may directly interact with their wild-type paralogs in the context of PD and ALS/FTD pathogenesis. Together, these findings demonstrate that differences in the stability and mutual affinity of CHCHD2 and CHCHD10 regulate their heterodimerization in response to mitochondrial distress, revealing an unanticipated link between PD and ALS/FTD pathogenesis.

Previous studies suggest prenatal methamphetamine (MA) exposure inhibits fetal growth. We examined neonatal growth effects of prenatal MA exposure in a prospective cohort study. After adjusting for covariates, exposed neonates had a higher incidence of being small for gestational age (SGA) than unexposed neonates. Keywords drug; amphetamine; antenatal; small for gestational age Methamphetamine is one of the primary illicit drugs of dependence in the United States, and its use among women continues to be a serious problem. Early studies have reported an association between prenatal MA exposure and decreased newborn growth. A study of 91 mother-infant pairs with positive urine toxicology screens at delivery reported that MA/ cocaine-exposed neonates had lower birth weights, smaller head circumferences and were more likely to be small for gestational age (SGA) than comparison neonates. 1 Growth deficits have also been reported in 65 MA-exposed children as old as 4 years.2 These previous reports were limited by small sample size, no adjustment for confounding factors, retrospective analysis1, no comparison group2, and reliance on hospital records1 or maternal

No abstract

Three metE mutations ofBacillus subtlis, which cause cells to have a 25-to 200-fold decrease in L-methionine S-adenosyltransferase (EC 2.5.1.6) activity, were mapped between bioB and thr. The corresponding three metE mutants contained three-to fourfold less intracellular S-adenosylmethionine (SAM) but at least sevenfold more methionine than the metE+ strain when grown in synthetic medium. This indicates a strong feedback control of SAM on its synthesis. However, only the metE2 strain, with the lowest SAM concentration, grew at a slightly lower rate than the parent, which showed that an intracellular concentration of about 25 ,uM SAM was critical for growth at the normal rate. Neither DNA methylation (measured by bacteriophage +105 restriction) nor sporulation was affected at this low SAM concentration. Addition of methionine to the growth medium caused an increase in the pool of SAM in some but not all metE mutants. Coaddition of adenine did not change this result. However, the extent of sporulation (induced by mycophenolic acid) was decreased 50-fold in all mutants by the addition of methionine and adenine. Therefore, the combination of methionine and adenine suppresses sporulation regardless of whether it causes an increase in the level of SAM.In previous work from this laboratory, exposure of a Bacillus subtilis relAl strain (strain 61885; for detailed genotypes, see Table 1) to ethionine (optimal concentration, 1 mM) greatly (104 fold) increased the sporulation frequency (in the presence of glucose, which normally represses sporulation) and caused a decrease in L-methionine S-adenosyltransferase (SAM synthetase; EC 2.5.1.6) activity (20). Cells of a "metEl" mutant (strain 62258), isolated by resistance to the methionine (Met) analog ethionine at 10 mM, had greatly decreased S-adenosylmethionine (SAM) synthetase activity and sporulated spontaneously (in the presence of glucose) at about a 10-fold-higher frequency than its parent (strain 61885) (20). The increased sporulation frequency apparently depended on the metEl mutation, because a transformant (strain 62302), isolated by transformation of a different relAl strain (strain 62262) with DNA of the "metEl" mutant (strain 62258) and plating on 10 mM ethionine, also showed elevated spontaneous sporulation (20). These results were interpreted as indicating that the decrease of SAM synthetase activity was responsible for the increased spontaneous sporulation. Furthermore, addition of SAM or of the SAM precursors Met and adenosine, greatly decreased this sporulation, suggesting that increased SAM levels in the cells may suppress sporulation (20).It was later realized that the original parent (strain 61885) already contained a mutation (called ethAl) which caused resistance to intermediate (2 mM) ethionine concentrations and was required for the continual sporulation caused by ethionine. The sporulation resulted from the production of S-adenosylethionine rather than from the decrease of intra-* Corresponding author. cellular SAM levels and did not simply depend on...

Whereas Parkinson disease (PD) is usually sporadic, PD with onset under 50 years old can be associated with genetic abnormalities, including rare biallelic mutations in the DJ1 gene (PARK7). 1 The DJ1 phenotype is incompletely described and has been presumed to be similar to the Parkin (PARK2) phenotype, in which atypical clinical features are usually absent, and, in contrast to idiopathic PD, synucleinopathy is lacking and olfaction preserved. 2 Whether DJ1 patients have peripheral synucleinopathy and olfactory dysfunction has been unknown.