Biallelic CRELD1 variants cause a multisystem syndrome, including neurodevelopmental phenotypes, cardiac dysrhythmias, and frequent infections

PURPOSE

We sought to delineate a multisystem disorder caused by recessive cysteine-rich with epidermal growth factor-like domains 1 (CRELD1) gene variants.

METHODS

The impact of CRELD1 variants was characterized through an international collaboration utilizing next-generation DNA sequencing, gene knockdown, and protein overexpression in Xenopus tropicalis, and in vitro analysis of patient immune cells.

RESULTS

Biallelic variants in CRELD1 were found in 18 participants from 14 families. Affected individuals displayed an array of phenotypes involving developmental delay, early-onset epilepsy, and hypotonia, with about half demonstrating cardiac arrhythmias and some experiencing recurrent infections. Most harbored a frameshift in trans with a missense allele, with 1 recurrent variant, p.(Cys192Tyr), identified in 10 families. X tropicalis tadpoles with creld1 knockdown displayed developmental defects along with increased susceptibility to induced seizures compared with controls. Additionally, human CRELD1 harboring missense variants from affected individuals had reduced protein function, indicated by a diminished ability to induce craniofacial defects when overexpressed in X tropicalis. Finally, baseline analyses of peripheral blood mononuclear cells showed similar proportions of immune cell subtypes in patients compared with healthy donors.

CONCLUSION

This patient cohort, combined with experimental data, provide evidence of a multisystem clinical syndrome mediated by recessive variants in CRELD1.

SPTSSA variants alter sphingolipid synthesis and cause a complex hereditary spastic paraplegia

Sphingolipids are a diverse family of lipids with critical structural and signalling functions in the mammalian nervous system, where they are abundant in myelin membranes. Serine palmitoyltransferase, the enzyme that catalyses the rate-limiting reaction of sphingolipid synthesis, is composed of multiple subunits including an activating subunit, SPTSSA. Sphingolipids are both essential and cytotoxic and their synthesis must therefore be tightly regulated. Key to the homeostatic regulation are the ORMDL proteins that are bound to serine palmitoyltransferase and mediate feedback inhibition of enzymatic activity when sphingolipid levels become excessive. Exome sequencing identified potential disease-causing variants in SPTSSA in three children presenting with a complex form of hereditary spastic paraplegia. The effect of these variants on the catalytic activity and homeostatic regulation of serine palmitoyltransferase was investigated in human embryonic kidney cells, patient fibroblasts and Drosophila. Our results showed that two different pathogenic variants in SPTSSA caused a hereditary spastic paraplegia resulting in progressive motor disturbance with variable sensorineural hearing loss and language/cognitive dysfunction in three individuals. The variants in SPTSSA impaired the negative regulation of serine palmitoyltransferase by ORMDLs leading to excessive sphingolipid synthesis based on biochemical studies and in vivo studies in Drosophila. These findings support the pathogenicity of the SPTSSA variants and point to excessive sphingolipid synthesis due to impaired homeostatic regulation of serine palmitoyltransferase as responsible for defects in early brain development and function.

Bi-allelic ATG4D variants are associated with a neurodevelopmental disorder characterized by speech and motor impairment

Autophagy regulates the degradation of damaged organelles and protein aggregates, and is critical for neuronal development, homeostasis, and maintenance, yet few neurodevelopmental disorders have been associated with pathogenic variants in genes encoding autophagy-related proteins. We report three individuals from two unrelated families with a neurodevelopmental disorder characterized by speech and motor impairment, and similar facial characteristics. Rare, conserved, bi-allelic variants were identified in ATG4D, encoding one of four ATG4 cysteine proteases important for autophagosome biogenesis, a hallmark of autophagy. Autophagosome biogenesis and induction of autophagy were intact in cells from affected individuals. However, studies evaluating the predominant substrate of ATG4D, GABARAPL1, demonstrated that three of the four ATG4D patient variants functionally impair ATG4D activity. GABARAPL1 is cleaved or "primed" by ATG4D and an in vitro GABARAPL1 priming assay revealed decreased priming activity for three of the four ATG4D variants. Furthermore, a rescue experiment performed in an ATG4 tetra knockout cell line, in which all four ATG4 isoforms were knocked out by gene editing, showed decreased GABARAPL1 priming activity for the two ATG4D missense variants located in the cysteine protease domain required for priming, suggesting that these variants impair the function of ATG4D. The clinical, bioinformatic, and functional data suggest that bi-allelic loss-of-function variants in ATG4D contribute to the pathogenesis of this syndromic neurodevelopmental disorder.

Continuing a search for a diagnosis: the impact of adolescence and family dynamics

The "diagnostic odyssey" describes the process those with undiagnosed conditions undergo to identify a diagnosis. Throughout this process, families of children with undiagnosed conditions have multiple opportunities to decide whether to continue or stop their search for a diagnosis and accept the lack of a diagnostic label. Previous studies identified factors motivating a family to begin searching, but there is limited information about the decision-making process in a prolonged search and how the affected child impacts a family's decision. This study aimed to understand how families of children with undiagnosed diseases decide whether to continue to pursue a diagnosis after standard clinical testing has failed. Parents who applied to the Undiagnosed Disease Network (UDN) at the National Institutes of Health (NIH) were recruited to participate in semi-structured interviews. The 2015 Supportive Care Needs model by Pelenstov, which defines critical needs in families with rare/undiagnosed diseases, provided a framework for interview guide development and transcript analysis (Pelentsov et al in Disabil Health J 8(4):475-491, 2015. https://doi.org/10.1016/J.DHJO.2015.03.009 ). A deductive, iterative coding approach was used to identify common unifying themes. Fourteen parents from 13 families were interviewed. The average child's age was 11 years (range 3-18) and an average 63% of their life had been spent searching for a diagnosis. Our analysis found that alignment or misalignment of parent and child needs impact the trajectory of the diagnostic search. When needs and desires align, reevaluation of a decision to pursue a diagnosis is limited. However, when there is conflict between parent and child desires, there is reevaluation, and often a pause, in the search. This tension is exacerbated when children are adolescents and attempting to balance their dependence on parents for medical care with a natural desire for independence. Our results provide novel insights into the roles of adolescents in the diagnostic odyssey. The tension between desired and realistic developmental outcomes for parents and adolescents impacts if, and how, the search for a diagnosis progresses.

Advances at TRIUMF-ISAC and decay of neutron-rich Cd studied with GRIFFIN

The β-decay half lives of nuclei near the r-process path are critical information required for abundance calculations, especially those near neutron number N = 82. Specifically, the nuclei below doubly-magic 132Sn are key, and play an important role in the formation and shape of the second r-process abundance peak. The half lives in this region are challenging to measure due to the significant β-delayed neutron decay branches and the population of isomeric states with half lives comparable to the ground states. However, by measuring the time distribution of γ rays, these complications can be eliminated. This requires, however, a very effcient γ-ray spectrometer since the production of isotopes in this region is very limited. The new GRIFFIN array at TRIUMF-ISAC provides the high effciency required for these measurements. Recent improvements in the quality of the beams produced at TRIUMF, employing the IG-LIS device, are outlined, as well as the current status of the ARIEL facility. The GRIFFIN spectrometer and its use are briefly described. The experiment to measure the half lives of 128-130Cd is outlined and the results given, and some examples of the power of GRIFFIN to expand decay schemes, specifically for the decay of 128Cd to 128In, are given.

Autocrine and paracrine Müllerian inhibiting substance hormone signaling in reproduction

Members of the transforming growth factor beta (TGFbeta) superfamily are polypeptide growth factors that exhibit diverse effects on normal cell growth, adhesion, mesenchymal-epithelial interactions, cell differentiation, and programmed cell death. This chapter will discuss the work of ourselves and others on one member of this large superfamily, Müllerian inhibiting substance (MIS, or anti-Müllerian hormone, AMH) and its role in reproductive tract development and the adult gonad. Using recombinant MIS protein, it is possible to begin unraveling the molecular mechanism of duct involution in the embryo. Our recent results suggest that MIS triggers cell death by altering mesenchymal-epithelial interactions. In addition to the developmental effects of MIS in secondary sexual differentiation, expression studies of the MIS ligand and the MIS type II receptor (MISIIR) suggest a potential regulatory role for MIS in adult germ cell maturation and gonadal function. Recent data from others suggest that MIS may act in a paracrine manner to block differentiation of interstitial cells of the adult gonad by repressing all or some steps of steroidogenesis. Our studies are highly suggestive of direct repression of steroidogenic enzyme gene expression by activation of the MIS signaling pathway. Thus, for the first time, an opportunity to define fully target genes and components of the MIS signaling pathway may be possible.

Bok is a pro-apoptotic Bcl-2 protein with restricted expression in reproductive tissues and heterodimerizes with selective anti-apoptotic Bcl-2 family members

In the intracellular death program, hetero- and homodimerization of different anti- and pro-apoptotic Bcl-2-related proteins are critical in the determination of cell fate. From a rat ovarian fusion cDNA library, we isolated a new pro-apoptotic Bcl-2 gene, Bcl-2-related ovarian killer (Bok). Bok had conserved Bcl-2 homology (BH) domains 1, 2, and 3 and a C-terminal transmembrane region present in other Bcl-2 proteins, but lacked the BH4 domain found only in anti-apoptotic Bcl-2 proteins. In the yeast two-hybrid system, Bok interacted strongly with some (Mcl-1, BHRF1, and Bfl-1) but not other (Bcl-2, Bcl-xL, and Bcl-w) anti-apoptotic members. This finding is in direct contrast to the ability of other pro-apoptotic members (Bax, Bak, and Bik) to interact with all of the anti-apoptotic proteins. In addition, negligible interaction was found between Bok and different pro-apoptotic members. In mammalian cells, overexpression of Bok induced apoptosis that was blocked by the baculoviral-derived cysteine protease inhibitor P35. Cell killing induced by Bok was also suppressed following coexpression with Mcl-1 and BHRF1 but not with Bcl-2, further indicating that Bok heterodimerized only with selective anti-apoptotic Bcl-2 proteins. Northern blot analysis indicated that Bok was highly expressed in the ovary, testis and uterus. In situ hybridization analysis localized Bok mRNA in granulosa cells, the cell type that underwent apoptosis during follicle atresia. Identification of Bok as a new pro-apoptotic Bcl-2 protein with restricted tissue distribution and heterodimerization properties could facilitate elucidation of apoptosis mechanisms in reproductive tissues undergoing hormone-regulated cyclic cell turnover.

Preantral ovarian follicles in serum-free culture: suppression of apoptosis after activation of the cyclic guanosine 3',5'-monophosphate pathway and stimulation of growth and differentiation by follicle-stimulating hormone

Progression of preantral follicle development is essential to further follicle maturation and ovulation, but there are few models for studying the regulation of preantral follicle survival and growth. We have evaluated preantral follicle survival in vivo and in vitro, and have developed a serum-free rat follicle culture system that can be used to characterize the regulation of preantral follicle growth and differentiation. Analysis of ovarian cell DNA fragmentation during the first wave of follicle growth in the infantile rat indicated negligible apoptosis up to day 16 of age. However, a major increase in apoptosis was found by day 18, a time point associated with the appearance of large antral follicles. In situ analysis confirmed that apoptotic DNA fragments were limited to antral follicles. Culture of individual preantral follicles mechanically dissected from ovaries of 12- or 14-day-old rats in serum-free conditions led to major increases in follicle cell apoptosis, similar to that seen in cultures of antral and preovulatory follicles. In contrast to antral and preovulatory follicles, treatment of preantral follicles with gonadotropins or cAMP analogs did not prevent apoptosis. However, treatment with 8-bromo-cGMP or 10% serum suppressed apoptosis by 75% in cultured preantral follicles. In situ analysis identified granulosa cells as the cell type susceptible to apoptosis regulation. Taking advantage of the ability of the cGMP analog to suppress apoptosis, we evaluated the potential of FSH as a growth factor. In the absence of serum, FSH treatment for 48 h did not affect follicle size compared to controls; however, treatment with the cGMP analog together with FSH increased follicle diameter (13%; P < 0.01) and viable cells (2.4-fold; P < 0.01) compared to control values. Immunoblot analysis further indicated that the inhibin-alpha content of the cultured follicles was increased by treatment with the combination of FSH and 8-bromo-cGMP, demonstrating the induction of follicle cell differentiation during culture. Therefore, we demonstrated that activation of the cGMP pathway promotes the survival of cultured preantral follicles and that in the presence of alpha cGMP analog, FSH is a growth and differentiation factor for preantral follicles. The present serum-free follicle culture model system will be useful in further evaluation of the regulation of growth and differentiation of preantral follicles.

Inhibin and activin differentially regulate androgen production and 17 alpha-hydroxylase expression in human ovarian thecal-like tumor cells

Activin and inhibin are structurally related dimeric glycoproteins belonging to the transforming growth factor-beta superfamily of proteins which are synthesized and secreted by the granulosa cells of the ovary. Although initially characterized by their ability to influence FSH secretion from pituitary cells, paracrine regulatory roles of these factors on neighboring ovarian theca interna have been suggested. While inhibin has been shown to increase and activin to decrease the production of androgens, the mechanisms of action are not well defined, partly due to difficulties in obtaining adequate numbers of thecal cells from individual patients or animal models. Using a unique human ovarian thecal-like tumor (HOTT) cell culture model system we investigated the biochemical and molecular mechanisms controlling C19 steroidogenesis and the effects of activin and inhibin on the activity and expression of key ovarian thecal steroidogenic enzymes, cholesterol side-chain cleavage cytochrome P450 (P450scc), 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) and 17 alpha-hydroxylase/17,20 lyase cytochrome P450 (P450c17). Steroid production, level of steroidogenic enzyme mRNA expression, and enzyme activity following treatment with forskolin, inhibin-A and activin-A were examined. Basal steroid production, enzyme activities, and steroidogenic enzyme mRNA levels were not markedly different following treatment with activin (25 ng/ml) or inhibin (25 ng/ml) alone. Forskolin (10 microM) markedly increased production of both androstenedione (fivefold) and progesterone (threefold) as well as the activity of 3 beta HSD (sevenfold), and P450c17 (sevenfold) over basal. Forskolin stimulated the expression of mRNA for P450scc (fourfold), 3 beta HSD (threefold), and P450c17 (eightfold) over basal. Androstenedione accumulation was decreased by 60% in the forskolin plus activin group compared with forskolin alone, while progesterone production was maintained. This was attributed to a reduction of P450c17 mRNA (45% of forskolin alone) and activity (45% of forskolin alone). In contrast, co-treatment with forskolin and inhibin increased androstenedione production by 40% while decreasing progesterone by 40% compared with forskolin alone. Concomitantly, this was associated with a higher P450c17 mRNA expression (1.5-fold) and activity (twofold) but with minimal effects on the mRNA for 3 beta HSD and P450scc. HOTT cell responses to activin (0.05-50 ng/ml) and inhibin (0.05-50 ng/ml) in the presence of forskolin demonstrated dose-dependent effects on the steroid accumulation, enzymatic activity and mRNA expression of P450c17. Additionally, the differences seen on mRNA expression of steroidogenic enzymes in response to these factors were time-dependent. In summary, forskolin stimulated C19 steroid production from HOTT cells by increasing the expression of all steroidogenic enzymes examined. Inhibin and activin exerted differential effects on the expression of these enzymes which resulted in alterations in the steroid profile toward production of C19 steroids in the case of inhibin and away from C19 steroids in the case of activin. The influence of these important intraovarian factors on the expression of P450c17, a pivotal enzyme in thecal cell production of C19 steroids, could impact greatly on the follicular milieu of a normal developing follicle as well as in pathophysiological disorders such as polycystic ovarian syndrome.

The effects of insulin on 3 beta-hydroxysteroid dehydrogenase expression in human luteinized granulosa cells

OBJECTIVE

We determined the relative effects of insulin and FSH on progesterone accumulation as well as activity, protein content, and mRNA expression of 3 beta-hydroxysteroid dehydrogenase (3 beta HSD) in human luteinized granulosa cells.

METHODS

Luteinized granulosa cells obtained from women undergoing in vitro fertilization were plated and grown to near confluence and treated with FSH, insulin, or a combination of insulin and FSH. Progesterone production as well as enzyme activity, protein content, and mRNA expression for 3 beta HSD were evaluated.

RESULTS

Progesterone production was not affected by insulin alone but increased threefold in the presence of FSH (50 ng/microL) alone. The presence of FSH plus insulin (100 nmol/L) caused a significant increase in progesterone accumulation greater than that of FSH alone. The already high basal levels of 3 beta HSD activity were unaffected by insulin alone but increased 1.7-fold in the presence of FSH. The combination of FSH (50 ng/mL) and insulin (100 nmol/L) increased activity 1.3-fold over FSH alone (P < .02). Insulin (greater than 100 nmol/L) alone increased 3 beta HSD protein content as measured by Western analysis 1.8-2-fold over basal levels, whereas FSH alone increased protein content 2.8-fold, and was further augmented by the addition of insulin in a dose-related fashion up to 3.5-fold over basal levels. Insulin increased 3 beta HSD mRNA twofold over basal levels; FSH alone increased mRNA expression of 3 beta HSD 3.2-fold. In the presence of insulin plus FSH, 3 beta HSD mRNA expression increased 7.6-fold over basal levels. For comparison, insulin also stimulated cytochrome P450 aromatase activity, P450 aromatase protein, and mRNA but to a greater degree than that seen for 3 beta HSD.

CONCLUSION

Insulin is a regulator of both 3 beta HSD and aromatase expression in human granulosa cells. Elevated insulin levels could therefore affect steroid production in human granulosa cells and presumably alter the menstrual cycle and fertility.

Nitrate Leaching in Dryland Agroecosystems as Influenced by Soil and Climate Gradients

Farmers in dryland agriculture areas of the Central Great Plains have characteristically practiced alternate crop-fallow to stabilize yields. Large amounts of N released soon after sodbreaking and more recent fertilizer additions may have contributed to N movement below crop root zones. Improved water conservation techniques during fallow periods increases the possibility of NO₃ leaching below root zones in modern-day crop-fallow systems. Soil topography and water supply may affect leaching potential. This study was conducted to test hypotheses regarding landscape position effects and potential evapotranspiration on depth of water and NO₃ penetration. Three sites in eastern Colorado with equal annual precipitation, but with mean potential evapotranspiration varying from 1000 to 1900 mm yr^-1 were evaluated. A soil catena was sampled at each site to test landscape effects. All sites were previously managed under tilled wheat-fallow systems for at least 50 yr. All summit (upland) sites had higher water and NO₃ contents below their crop root zones than nearby native prairie sites. Soil water and NO₃ content of soil profiles to a depth of 9 m were not related to slope position, but there was an inverse relationship between water and NO₃ content of soil profiles and potential evapotranspiration. The total NO₃ -N in cultivated profiles below the normal root zone of crops varied from 126 kg ha^-1 at the northern site to 47 kg ha^-1 at the southern site. Although some NO₃ leaching had occurred, it did not appear to be a major problem for any particular landscape position or climatic zone on cultivated soils.

Genetic relationships of European populations reflect their ethnohistorical affinities

From 420 records of ethnic locations and movements since 2000 B.C., we computed vectors describing the proportions which peoples of the various European language families contributed to the gene pools within 85 land-based 5 x 5-degree quadrats in Europe. Using these language family vectors, we computed ethnohistorical affinities as arc distances between all pairs of the 85 quadrats. These affinities are significantly correlated with genetic distances based on 26 genetic systems, even when geographic distances, a common causative factor, are held constant. Thus, the ethnohistorical distances explain a significant amount of the genetic variation observed in modern populations. Randomizations of the records by chronology result in loss of significance for the observed partial correlation between genetics and ethnohistory, when geography is held constant. However, a randomization of records by location only results in reduced significance. Thus, while the historical sequence of the movements does not seem to matter in Europe, their geographic locations do. We discuss the implications of these findings.

The effect of gonadotropin-releasing hormone agonists on adrenocorticotropin and cortisol secretion in adult premenopausal women

GnRH agonists are known to suppress LH, FSH, and subsequent ovarian estradiol production by down-regulation of pituitary gonadotropin receptors. Previous investigations have demonstrated that GnRH agonists also suppress GHRH-stimulated GH release in normal men and women and PRL levels in subjects with hyperprolactinemia. Little is known about the effects of GnRH agonists on the hypothalamic-pituitary-adrenal axis. The purpose of the present investigation was to determine the secretion of ACTH and cortisol after an iv infusion of hCRH in control women (n = 11) and in women undergoing treatment with GnRH agonists (n = 10). The plasma and serum levels of ACTH and cortisol increased after infusion of CRH in all women. The basal and CRH-stimulated plasma levels of ACTH and cortisol at each time point were not statistically different between GnRH agonist-treated women and controls. Thus, the chronic use of GnRH agonists is known to suppress the hypothalamic-pituitary-ovarian axis and is associated with GH and PRL suppression as well, but does not apparently alter the hypothalamic-pituitary-adrenal axis.

A straightforward radiometric technique for measuring IMP dehydrogenase

[2-3H]Inosinic acid ([2-3H]IMP) has been biosynthesized in good yield from [2-3H]hypoxanthine and PRPP via the action of a partially purified preparation of hypoxanthine/guanine phosphoribosyl transferase from mouse brain. The product was purified in one step by ascending paper chromatography, and used to assess the activity of IMP dehydrogenase. To conduct the assay, tritiated substrate is admixed with enzyme in a final volume of 10 microliters; NAD is present to serve as cofactor for the reaction, and allopurinol to inhibit the oxidation of any hypoxanthine generated as a consequence of side reactions. After an appropriate period of incubation, the 3H2O arising from the oxidation of tritiated IMP via [3H]NAD is isolated by quantitative microdistillation. Performed as described, the assay is facile, sensitive, and accurate, with the capability of detecting the dehydrogenation of as little as 1 pmol of [3H]IMP. Using it, measurements have been made of IMP dehydrogenase in a comprehensive array of mouse organs. Of these, pancreas contained the enzyme at the highest specific activity.

Determinants of the toxicity of L-alanosine to various organs of the mouse

Toxicologic and biochemical properties of the antitumor antibiotic, alanosine [L-2-amino-3-(N-hydroxy,N-nitrosamino)propionic acid], were studied in mice. The LD50 of L-alanosine (given intraperitoneally) was approximately 2 g/kg; L-5178Y/AR tumor, small intestine, liver, and lung were the tissues more consistently or severely damaged by the drug. L-5178Y/AR tumor, small intestine, liver, and lung, which were more susceptible to damage by L-alanosine, showed high concentrations of the putative active antimetabolite of L-alanosine, "L-alanosyl-AICOR", and either high concentrations of SAICAR synthetase, which forms this conjugate or low specific activities of adenylosuccinate lyase, the enzyme believed to decompose it. In addition, a low specific activity of the enzyme, adenylosuccinate synthetase, appeared to predispose an organ to the toxicity of alanosine. These data are compatible with the hypothesis that "L-alanosyl-AICOR" is the molecule responsible both for the therapeutic and toxicologic effects of L-alanosine and suggest that it is the dynamic interplay of the synthesizing enzyme, the catabolizing enzyme, and the target enzyme which determines whether this anabolite accumulates to a concentration capable of inflicting cellular damage.