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About Richard J. Richard J. Schneider is the creator of the Vic Bengston Investigation mystery series, set in Colorado. Vic is a Baby Boomer who returns to investigative journalism after a few decades running a public relations business. In WATER, the first in the series, Vic signals his return to Denver journalism with a front page splash on the execution-style murder of a well-known political figure.
But he is p Richard J. This does not stop Vic, who bucks his bosses and the cops to unravel the mystery, eventually leading to a deadly confrontation with the killer.
The next in the series, VOTE, will be available in early He follows hunches, and breaks the rules. On brain MRI see Figure 1 :. Central white matter structures, including the corpus callosum, internal capsule, and brain stem, are better preserved than other structures, although they are not usually entirely normal. Subcortical cysts are almost invariably present in the anterior temporal region and often in the frontoparietal region. Over time, the white matter swelling decreases and cerebral atrophy ensues.
The subcortical cysts may increase in size and number. In some individuals, the cysts become huge, occupying a large part of the frontoparietal white matter. In others, the cerebral white matter abnormalities decrease over time, and the signal intensity of the cerebral white matter becomes less abnormal.
Diffusion-weighted imaging reveals increased diffusivity of abnormal white matter [ Itoh et al , van der Voorn et al ].
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Figure 1. Macrocephaly onset in the first year of life or congenital macrocephaly. Findings within the first year of life are similar to those seen in the classic phenotype , but cerebellar white matter is usually normal in signal. Striking improvement occurs over time. The MRI may appear normal within a few years, or minor frontal and temporal subcortical white matter abnormalities and anterior temporal cysts may remain.
Table 1. Genes are listed alphabetically. Clinical Characteristics Clinical Description The two phenotypes observed in individuals with megalencephalic leukoencephalopathy with subcortical cysts MLC include the classic phenotype and the improving phenotype. Improving Phenotype MLC2B In children diagnosed with MLC2B the initial disease course is the same as that in children with the classic phenotype : mental and motor development is normal in most and mildly delayed in some.
Penetrance MLC2B. Nomenclature Names previously used for MLC: Leukoencephalopathy with swelling and a discrepantly mild course. Prevalence Megalencephalic leukoencephalopathy with subcortical cysts is a rare disorder with a low carrier rate in the general population. Almost all East Indian individuals with MLC1 belong to the Agrawal community; and all individuals within this community are biallelic for the same pathogenic variant c. One common pathogenic variant c. The same variant was identified in several affected individuals from a single Turkish Jewish family descended from the same ancestors.
Screening of normal Libyan Jewish individuals for this particular pathogenic variant revealed a carrier rate of one in 40, as compared with an expected carrier rate of one in Non-Jewish Turkish individuals do not share a common pathogenic variant. The MLC1 pathogenic variant c. In Korea, c. Genetically Related Allelic Disorders Associations of MLC1 variants with catatonic schizophrenia have been reported, but whether they have a role in development of this phenotype remains to be determined [ Meyer et al , Devaney et al , Rubie et al , Kaganovich et al , Verma et al , Selch et al , Spijker et al , Balestri et al ].
Differential Diagnosis The differential diagnosis of macrocephaly and a diffuse leukoencephalopathy is limited; it includes Canavan disease, Alexander disease, infantile-onset GM2 gangliosidosis, and, on occasion, infantile-onset GM1 gangliosidosis and Lhydroxyglutaric aciduria.
Table 2. Typical involvement of brain stem structures signal abnormalities, tumor-like structures, atrophy not seen in MLC. Dentate nucleus typically prominently affected not in MLC. Management Evaluations Following Initial Diagnosis To establish the extent of disease in an individual diagnosed with megalencephalic leukoencephalopathy with subcortical cysts MLC the following evaluations are recommended if they have not already been completed: Neurologic examination.
Treatment of Manifestations Supportive therapy includes the following: Physical therapy to improve motor function. Prevention of Secondary Complications If patients have epilepsy, treatment with antiepileptic drugs should be considered. Surveillance There are no published guidelines for surveillance. Evaluation of Relatives at Risk See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes. Pregnancy Management Potential teratogenic effects of antiepileptic drugs should be discussed with affected women of childbearing age, ideally prior to conception.
Other Unsuccessful therapies have included diuretics, acetazolamide, and creatine monohydrate. Genetic Counseling Genetic counseling is the process of providing individuals and families with information on the nature, inheritance, and implications of genetic disorders to help them make informed medical and personal decisions.
Heterozygotes carriers are asymptomatic. Intrafamilial variability has been observed in MLC1. Heterozygotes carriers are asymptomatic and are not at risk of developing the disorder. Given the neurologic improvement that is observed in this phenotype , the parent is not at risk of neurologic regression. Whether having a heterozygous HEPACAM pathogenic variant leads to other symptoms late in life has not been investigated; however, to date no evidence suggests disease progression later in life.
A proband with MLC2B may have the disorder as the result of a de novo pathogenic variant. Recommendations for the evaluation of parents of a proband with an apparent de novo pathogenic variant include molecular genetic testing. If the pathogenic variant found in the proband cannot be detected in leukocyte DNA of either parent, two possible explanations are a de novo pathogenic variant in the proband or germline mosaicism in a parent. Though theoretically possible, no instances of germline mosaicism have been reported.
The family history of some individuals diagnosed with MLC2B may appear to be negative because of failure to recognize the disorder in family members, reduced penetrance , or milder phenotypic presentation. The risk to the sibs of the proband depends on the genetic status of the proband's parents. If the parents have not been tested for the MLC2B-related pathogenic variant but are clinically unaffected, the sibs are still at increased risk for MLC2B because of the possibility of reduced penetrance in a parent or the theoretic possibility of parental germline mosaicism.
Related Genetic Counseling Issues Family planning The optimal time for determination of genetic risk, clarification of carrier status, and discussion of the availability of prenatal testing is before pregnancy. It is appropriate to offer genetic counseling including discussion of potential risks to offspring and reproductive options to young adults who are affected , are carriers, or are at risk of being carriers.
Prenatal Testing and Preimplantation Genetic Diagnosis Once the pathogenic variant s have been identified in an affected family member, prenatal testing for a pregnancy at increased risk and preimplantation genetic diagnosis for MLC are possible. Table A. Table B. Table 3. Gly59Glu c. Ser93Leu c. Thr99fsTer c. AlaAsp c. Table 4. Gly89Ser c. Metab Brain Dis. Hum Mutat. Nine differentially expressed genes from a post mortem study and their association with suicidal status in a sample of suicide completers, attempters and controls.
J Psychiatr Res. Vacuolating megalencephalic leukoencephalopathy in 12 Israeli patients. J Child Neurol. Megalencephalic leukoencephalopathy with subcortical cysts; a founder effect in Israeli patients and a higher than expected carrier rate among Libyan Jews. Hum Genet. MLC1 is associated with the dystrophin-glycoprotein complex at astrocytic endfeet. Acta Neuropathol. MLC1 protein: a likely link between leukodystrophies and brain channelopathies.
Front Cell Neurosci. Megalencephalic leukoencephalopathy with cysts: the Glialcam -null mouse model. Ann Clin Transl Neurol. Consciousness disturbances in megalencephalic leukoencephalopathy with subcortical cysts. Ten novel mutations in Chinese patients with megalencephalic leukoencephalopathy with subcortical cysts and a long-term follow-up research. PLoS One. Hum Mol Genet. A unique mutational spectrum of MLC1 in Korean patients with megalencephalic leukoencephalopathy with subcortical cysts.
Ann Lab Med. Cloning and characterization of hepaCAM, a novel Ig-like cell adhesion molecule suppressed in human hepatocellular carcinoma. J Hepatol. No missense mutation of WKL1 in a subgroup of probands with schizophrenia. Mol Psychiatry. Neurobiol Dis. Seizures and disturbed brain potassium dynamics in the leukodystrophy megalencephalic leukoencephalopathy with subcortical cysts. Ann Neurol. Mice with megalencephalic leukoencephalopathy with cysts: a developmental angle. GlialCAM, an immunoglobulin-like cell adhesion molecule is expressed in glial cells of the central nervous system.
Indian Agarwal megalencephalic leukodystrophy with cysts is caused by a common MLC1 mutation. Nat Commun. Megalencephalic leukoencephalopathy with subcortical cysts: an update and extended mutation analysis of MLC1. Eur Neurol. Is the WKL1 gene associated with schizophrenia? Eight novel mutations in MLC1 from 18 Iranian patients with megalencephalic leukoencephalopathy with subcortical cysts. Eur J Med Genet. Identification of novel mutations in MLC1 responsible for megalencephalic leukoencephalopathy with subcortical cysts.
Am J Hum Genet. Mutant GlialCAM causes megalencephalic leukoencephalopathy with subcortical cysts, benign familial macrocephaly, and macrocephaly with retardation and autism. A missense mutation in a novel gene encoding a putative cation channel is associated with catatonic schizophrenia in a large pedigree. Vacuolating megalencephalic leukoencephalopathy with subcortical cysts: functional studies of novel variants in MLC1. Timing, rates and spectra of human germline mutation. Nat Genet. Megalencephalic leucoencephalopathy with cysts: defect in chloride currents and cell volume regulation.
MLC1 polymorphisms are specifically associated with periodic catatonia, a subgroup of chronic schizophrenia. Biol Psychiatry. MLC1 mutations in Japanese patients with megalencephalic leukoencephalopathy with subcortical cysts. Figure 9. Axes notations give the proportion of variance explained on each coordinate in percent.
This analysis indicates i a distinctly different microbial community between soil pools rhizosphere soil, bulk soil and litter, and ii that N addition affects not only community structure in hyphae-only litter compartments, but also in soil compartments cf.
Based on PLFA analysis, N addition to the litter compartment significantly decreased 13 C transfer to Actinobacteria and other Gram-positive bacteria, on a per g dry weight basis Figure This is caused by a reduction in biomass of the respective groups Figure 8 combined with a constant or decreased relative enrichment of 13 C Figure S5 , Table S2.
This indicates that, in addition to a loss of biomass, N treatment also affected the transfer of recent photosynthates to hyphosphere bacteria. Figure However, correspondence analysis shows no effect of N addition on relative 13 C enrichment Figure S6.
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Moreover, we did not observe a significant effect of N addition on relative 13 C enrichment in microbial biomass based on CFE Table 2. The release of recent plant photosynthates into the soil has been shown to accelerate microbial decomposition of soil organic matter Kuzyakov et al. Very little, however, is known about a possible transfer of recent photosynthates to soil via ECM fungi, and interactions of ECM fungi with soil bacteria.
Here, we provide evidence that plant-photoassimilated C is rapidly transferred to root-distant soil bacteria via ECM hyphae, indicating that ECM fungi readily share this resource with soil saprotrophs. Contrary to our hypothesis, however, the addition of labile N did not result in increased hyphal C transfer to bacteria.
Instead, bacterial biomass and its incorporation of recent photosynthates declined with N addition not only in the litter compartment to which N was added, but also in adjacent untreated soil compartments, indicating a complex response of fungal-bacterial interactions to changing N availabilities.
Recent photosynthates were transferred to root-inaccessible areas in our system within hours. This transport of plant-derived C into litter compartments was most likely restricted to fungal hyphae, as our experimental design prevented diffusion and penetration of roots into the litter compartment by means of a double-layer mesh with an air-filled gap that could only be penetrated by hyphae.
Furthermore, NanoSIMS imaging provided evidence of significant 13 C enrichment inside a fungal hypha obtained from the litter compartment Figure 5. The similarity of ECM fungal communities in rhizosphere and litter compartments, together with the near absence of ECM fungal communities in litter compartments of unplanted boxes Figure 2 , strongly indicates a vital connection between plant roots and associated litter compartments by mycorrhizal hyphae.
While some transfer of recently plant-assimilated 13 C to the litter compartment via saprotrophic fungi cannot be ruled out, it is considered to be negligible because of the high degree of mycorrhization which likely prevents high rates of root exudation and the short time scales considered. Saprotrophic fungi are known to use complex organic matter as their main C source, rendering them unlikely to introduce substantial amounts of labile root exudates into the litter compartment within short time scales.
Megalencephalic Leukoencephalopathy with Subcortical Cysts - GeneReviews® - NCBI Bookshelf
We therefore assume that C transport via ECM hyphae accounted for the largest fraction of 13 C allocated to the litter compartment. While it is impossible to identify its phylogenetic identity, this strongly indicates that this hypha was mycorrhizal, as other, not plant-associated fungi would not be able to acquire that much plant-photoassimilated C in such a short time.
Providing free-living saprotrophs with low-molecular-weight C compounds to supplement their energy demand is a potentially viable strategy for ECM fungi to accelerate decomposition of recalcitrant organic matter. We provide evidence for a direct, short-term transfer of recent photosynthates i. This is supported by significant 13 C-enrichment not only of a bacteria-specific PLFAs in a compartment only accessible by fungal hyphae Figures 4 , 10 , but also b hyphae-attached microbial cells as visualized by NanoSIMS Figure 7.
Together with the fact that DOC was significantly 13 C-enriched, this indicates consumption of 13 C-enriched exudates by hyphae-associated microbes and incorporation of this C into cellular biomass. This study is the first one visualizing the incorporation of stable isotope labeled plant-derived C from ECM fungal hyphae into hyphae-associated microorganisms.
Another explanation for the 13 C enrichment of bacteria in litter compartments could be the acquisition of 13 C by saprotrophic microbes feeding on ECM hyphal necromass. This appears however likely negligible within the short period between the onset of 13 C-CO 2 pulse labeling and harvest, since the turnover rate estimates for ECM hyphae in natural systems range from weeks to several months Ekblad et al.
Unexpectedly, there was no preference in C transfer to specific bacterial groups, neither in the rhizosphere nor in the litter compartment as far as the resolution of the PLFA method allowed to trace this. Interestingly, the relative 13 C enrichment of bacterial PLFA biomarkers was as high, or even higher in the litter compartment than in rhizosphere or bulk soil, while relative 13 C enrichment of the fungal biomarker w6,9 strongly decreased from rhizosphere soil to the litter compartment.
Furthermore, bacteria incorporated the highest absolute amounts of 13 C in the litter compartment untreated side in Figure Together, this suggests higher hyphal C exudation in litter compared to soil compartments, indicating that bacteria received more C via the mycorrhizal hyphal pathway in the litter compartment than via combined root and mycorrhizal hyphal exudation in the rhizosphere.
ECM fungal hyphae are known to increase branching and growth when they reach organic-rich substrates Agerer, , , which may have happened in our litter compartments. Such a growth pattern would tremendously increase the mycelial surface area and number of hyphal tips Katz et al. Here, we demonstrate the transfer of labeled compounds from fungi to soil microbes in an ECM system by a spatially explicit approach, which provides insight into the local aspects of this interaction, and allows the in situ visualization of the stable isotope composition of microbial cells associated with fungal hyphae via NanoSIMS analysis.
While NanoSIMS represents a promising topochemical analysis technique to study C and nutrient transfer in fungal-bacterial interactions, it has only been used in a few studies for this purpose so far. Worrich et al. In a pioneering effort of visualizing microscale rhizosphere C flow through an undisturbed plant-soil system, Vidal et al. They found, amongst other results, a 13 C enriched spot, presumably a bacterial cell, on a fungal hypha associated with a wheat root.
However, due to the long-term labeling approach, this finding can't be attributed to a hyphal transfer of recently assimilated plant C to microbial cells which was also not the aim of that study , but may reflect accumulation of plant-derived organic C in soil bacteria over various pathways and longer time scales.
The addition of 15 N-labeled labile N compounds affected microbial community structure within days, causing a loss of biomass of certain bacterial groups. Potential reasons for this could be i the higher precision of PLFA analysis compared to CFE or ii differences in the target of the two methods. Phospholipids mainly occur in cell membranes, thus emphasizing cell surface areas in PLFA measurements, while CFE lyses cells with the lysate being proportional to cell volumes. For example, if a deteriorating effect on microbial biomass affected small microbial cells e.
This possibility is indirectly supported by PLFA analysis which also indicated a community shift in response to N addition. The strong and very rapid negative effect of labile N on bacterial biomass seems counter-intuitive, as we would rather expect a positive effect of N on bacterial growth. The amount of N we have added 0. However, the negative effect on microbial biomass was not restricted to the litter compartments, which received labile N inputs, but it also significantly affected the soil compartments separated from them by the hyphal-penetrable mesh.
As this represents only a negligible increase, we can rule out a direct effect of enhanced N availability on microbial biomass and community structure. As the effect however clearly took place not only in the litter, but also in the adjacent soil compartments, we can only speculate that it must have been caused by a systemic reaction of the fungi or the plant to altered local availability of N. If it was a fungal reaction it would be restricted to those fungi growing in the N-treated side of the box, i. If it was a plant reaction, it needed to have been directed toward the part of the root system that received more N.
One possible mechanism could be that when ECM fungi were exposed to easily available N in excess, their interaction with associated bacteria drastically changed from cooperative to competitive. The latter could have happened in different ways, for example by reducing the input of labile C, which may be vital for parts of the bacterial community, or by actively employing allelopathic strategies, such as the production of antibiotics.
In fact, fungi are known to produce a plethora of bacterial and fungal antibiotics Keller et al. Furthermore, bacteria of the genus Streptomyces Actinobacteria , which is the largest antibiotic-producing bacterial genus known Watve et al. ECM fungi thus seem to have the potential to take allelopathic actions against bacterial saprotrophs when they switch to a competitive situation. To test if this actually happens goes however beyond the scope of this study and warrants further research.
As another option, ECM fungi may have reduced the transfer of plant-derived C to their bacterial competitors. As bacterial and fungal PLFA biomarkers received significantly lower amounts of 13 C, but 13 C enrichment in DOC was unchanged, we conclude that in total less 13 C was transferred via mycorrhizal hyphae to the litter compartment after addition of N Table 2.
An analogous reaction is often observed in plants, where C allocation to the rhizosphere decreases with N fertilization Kuzyakov and Domanski, The question remains whether a decrease in labile C input could have led to such a rapid decline in bacterial biomass, which seems unlikely to be caused just by starvation of bacterial cells. High turnover rates are defined as fast growth rates balanced by high mortality rates.
In an environment not limited by substrate availability, mortality is likely driven by density dependent mechanisms, such as predation, virus activity, or negative bacterial interactions West et al. It is thus possible that diminishing substrate input decreases bacterial growth rates, but mortality rates may stay high until population density has substantially decreased, which may also explain the rapid decline in microbial biomass.
While our results indicate that N availability affects the relationship of mycorrhizal fungi and soil microbes, it has to be kept in mind that we added only easily available forms of N, and only at a single concentration. The system may have responded in a different way if other quantities or qualities of N, such as complex organic N, were added. While this would be interesting to investigate, it goes beyond the scope of this study. Our results show a transfer of recent photosynthates via ECM hyphae to associated soil microbes in root-inaccessible areas within hours, supporting the hypothesis of priming in an ECM hyphosphere as a potential mechanism to increase access to nutrients from soil organic matter for ECM fungi and their host plants.
Contrary to our expectations, elevated local availability of labile N compounds did not result in higher hyphal exudation rates. Instead, we found a strong decline in biomass of Actinobacteria and other Gram-positive bacteria in response to N addition. This decline seems to have been caused by ECM fungi acting on soil bacteria, as the effect was observed in soil compartments where fertilized N would only be available for bacteria through hyphal transport. It is likely that fungi occupy the more sustained position in such an opportunistic mutualism, by controlling C flow to bacteria.
Accordingly, hyphosphere priming may be a highly controlled process with hyphal exudation being rapidly adjusted to changing soil nutrient availabilities. CK conceived and coordinated the study. SG and SE analyzed the data. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We thank the three reviewers for constructive comments which helped to improve the quality of the manuscript. Agerer, R. Exploration types of ectomycorrhizae.
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Kaiser, C. Plants control the seasonal dynamics of microbial N cycling in a beech forest soil by belowground C allocation.
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