Ciliopathies are a group of disorders caused by defects of the cilia. Joubert syndrome (JBTS) is a recessive and pleiotropic ciliopathy that causes cerebellar vermis hypoplasia and psychomotor delay. ...Although the intraflagellar transport (IFT) complex serves as a key module to maintain the ciliary structure and regulate ciliary signaling, the function of IFT in JBTS remains largely unknown. We aimed to explore the impact of IFT dysfunction in JBTS.
Exome sequencing was performed to screen for pathogenic variants in IFT genes in a JBTS cohort. Animal model and patient-derived fibroblasts were used to evaluate the pathogenic effects of the variants.
We identified IFT74 as a JBTS-associated gene in three unrelated families. All the affected individuals carried truncated variants and shared one missense variant (p.Q179E) found only in East Asians. The expression of the human p.Q179E-IFT74 variant displayed compromised rescue effects in zebrafish ift74 morphants. Attenuated ciliogenesis; altered distribution of IFT proteins and ciliary membrane proteins, including ARL13B, INPP5E, and GPR161; and disrupted hedgehog signaling were observed in patient fibroblasts with IFT74 variants.
IFT74 is identified as a JBTS-related gene. Cellular and biochemical mechanisms are also provided.
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Higher multiplexing in droplet digital PCR (ddPCR) can simplify the detection process of ddPCR-based non-invasive prenatal testing (NIPT) and improve its reliability, making it a practical approach ...in clinical practice. However, a high level of multiplex ddPCR-based NIPT has rarely been reported. In this study, we developed a multiplex ddPCR assay using universal locked nucleic acid (LNA) probes to reliably identify fetal aneuploidies. We first performed statistical analysis based on the Poisson distribution to evaluate the required number of target DNA molecules and the total number of droplets for a ddPCR assay. Next, we designed two sets of primers and probes to quantify cfDNA from chromosomes 21 and 18 and then determined the disease status of a sample. Finally, we evaluated our multiplex ddPCR assay with 60 clinical plasma samples. All of the 60 clinical samples were correctly identified. The accessibility and cost-effectiveness of our multiplex ddPCR-based NIPT make it a competitive prenatal testing method in clinical use.
Abstract
Methylmalonic acidemia (MMA)-affected patients may have developmental, hematological, neurological, metabolic, ophthalmological, and dermatological clinically abnormal findings. This study ...aimed to identify mutations in 13 Chinese MMA cases. We provided genetic counseling, treatment, and prenatal diagnosis for the families with MMA. Liquid chromatography-tandem mass spectrometry (LC–MS/MS) was performed and the results were confirmed by gas chromatography and mass spectrometry (GC/MS). Variant screening in probands was performed by targeted next-generation sequencing. Identified variants were confirmed by Sanger sequencing. Of these 13 MMA cases, seven were isolated MMA, and among them, six were caused by variants in
MMUT
and one was caused by a variant in
MCEE
. The other six cases were MMA with homocystinuria, which was caused by variants in
MMACHC
. We found six novel variants in three MMA-causing genes as follows: c.2008G>A, c.301_302insTA, c.984delC, and c.319A>T of
MMUT
; c.445T>C of
MMACHC
; and c.296T>C of
MCEE
. We provided prenatal diagnosis for two families with MMA at their next pregnancy, and one family had a healthy newborn. In conclusion, our findings expand the spectrum of genotypes in MMA. Effective genetic counseling is required to allow awareness of the patients’ families that MMA disease is treatable and a good prognosis can be obtained.
Deltamethrin (DLT) is effective against a broad spectrum of insects. Exposure to DLT has been demonstrated to cause oxidative stress. However, the mechanism of oxidative stress induced by DLT is ...little known. Groups of rats were gavaged with DLT once daily for 7 days at six dosages: 0, 2, 5, 10, 20, 40 mg/kg. The intensity of neurotoxicity and liver dysfunction caused by DLT were significantly increased in a dose-dependent manner. We found that DLT caused the increase of cytosolic superoxide in tissues. Western blot analysis showed that both the expression of p66shc and Ser36 phosphorylated p66shc, which were involved in ROS generation, were increased in tissues treated with DLT. Further investigation showed that DLT treatment resulted in the increase of intracellular ROS accompanied with elevated p66shc expression in different cell lines. And treatment of cells with DLT induced p66shc phosphorylation at Ser36 and the translocation of p66shc from cytoplasm to mitochondria. Moreover, the overexpression of wildtype p66shc caused the increase of DLT-mediated ROS level in SH-SY5Y cells, but cells overexpressing p66shcSer36Ala mutant plasmid had the opposite effect. And p66shc suppression by siRNA blunted DLT-mediated ROS generation. Taken together, our findings indicated p66shc mediated DLT-induced oxidative stress, which may be partly responsible for toxic effects.
•The intensity of neurotoxicity and liver dysfunction were significantly increased during 7-day DLT treatment.•DLT caused the increase of cytosolic superoxide and activation of p66shc in tissues.•P66shc mediated DLT-induced oxidative stress in vitro.
Abstract
Hereditary hearing loss is genetically heterogeneous, with diverse clinical manifestations. Here we performed targeted genome sequencing of 227 hearing loss related genes in 1027 patients ...with bilateral hearing loss and 520 healthy volunteers with normal hearing to comprehensively identify the molecular etiology of hereditary hearing loss in a large cohort from China. We obtained a diagnostic rate of 57.25% (588/1027) for the patients, while 4.67% (48/1027) of the patients were identified with uncertain diagnoses. Of the implicated 35 hearing loss genes, three common genes, including
SLC26A4
(278/588),
GJB2
(207/588),
MT-RNR1
(19/588), accounted for 85.54% (503/588) of the diagnosed cases, while 32 uncommon hearing loss genes, including
MYO15A
,
MITF
,
OTOF
,
POU3F4
,
PTPN11
, etc. accounted for the remaining diagnostic rate of 14.46% (85/588). Apart from Pendred syndrome, other eight types of syndromic hearing loss were also identified. Of the 64 uncertain significant variants and 244 pathogenic/likely pathogenic variants identified in the patients, 129 novel variants were also detected. Thus, the molecular etiology presented with high heterogeneity with the leading causes to be
SLC26A4
and
GJB2
genes in the Chinese hearing loss population. It’s urgent to develop a database of the ethnicity-matched healthy population as well as to perform functional studies for further classification of uncertain significant variants.
Phenylketonuria (PKU) is an autosomal recessive congenital metabolic disorder caused by PAH variants. Previously, approximately 5% of PKU patients remained undiagnosed after Sanger sequencing and ...multiplex ligation-dependent probe amplification. To date, increasing numbers of pathogenic deep intronic variants have been reported in more than 100 disease-associated genes.
In this study, we performed full-length sequencing of PAH to investigate the deep intronic variants in PAH of PKU patients without definite genetic diagnosis.
We identified five deep intronic variants (c.1199+502A>T, c.1065+241C>A, c.706+368T>C, c.706+531>C, and c.706+608A>C). Of these, the c.1199+502A>T variant was found at high frequency and may be a hotspot PAH variant in Chinese PKU. c.706+531T>C and c.706+608A>C are two novel variants that extend the deep intronic variant spectrum of PAH.
Deep intronic variant pathogenicity analysis can further improve the genetic diagnosis of PKU patients. In silico prediction and minigene analysis are powerful approaches for studying the functions and effects of deep intronic variants. Targeted sequencing after full-length gene amplification is an economical and effective tool for the detection of deep intron variation in genes with small fragments.
KIAA0586, also known as Talpid3, plays critical roles in primary cilia formation and hedgehog signaling in humans. Variants in KIAA0586 could cause some different ciliopathies, including Joubert ...syndrome (JBTS), which is a clinically and genetically heterogeneous group of autosomal recessive neurological disorders.
A 9-month-old girl was diagnosed as JBTS by the "molar tooth sign" of the mid-brain and global developmental delay. By whole-exome sequencing, we identified a single nucleotide variant c.3303G > A and a 1.38-kb deletion in KIAA0586 in the proband. These two variants of KIAA0586 were consistent with the mode of autosomal recessive inheritance in the family, which was verified using Sanger sequencing.
This finding of a compound heterozygote with a 1.38-kb deletion and c.3303G > A gave a precise genetic diagnosis for the patient, and the novel 1.38-kb deletion also expanded the pathogenic variation spectrum of JBTS caused by KIAA0586.
The mutation of K‐RAS represents one of the most frequent genetic alterations in cancer. Targeting of downstream effectors of RAS, including of MEK and ERK, has limited clinical success in cancer ...patients with K‐RAS mutations. The reduced sensitivity of K‐RAS‐mutated cells to certain MEK inhibitors (MEKi) is associated with the feedback phosphorylation of MEK by C‐RAF and with the reactivation of mitogen‐activated protein kinase (MAPK) signaling. Here, we report that the RAF dimer inhibitors lifirafenib (BGB‐283) and compound C show a strong synergistic effect with MEKi, including mirdametinib (PD‐0325901) and selumetinib, in suppressing the proliferation of K‐RAS‐mutated non‐small‐cell lung cancer and colorectal cancer (CRC) cell lines. This synergistic effect was not observed with the B‐RAFV600E selective inhibitor vemurafenib. Our mechanistic analysis revealed that RAF dimer inhibition suppresses RAF‐dependent MEK reactivation and leads to the sustained inhibition of MAPK signaling in K‐RAS‐mutated cells. This synergistic effect was also observed in several K‐RAS mutant mouse xenograft models. A pharmacodynamic analysis supported a role for the synergistic phospho‐ERK blockade in enhancing the antitumor activity observed in the K‐RAS mutant models. These findings support a vertical inhibition strategy in which RAF dimer and MEKi are combined to target K‐RAS‐mutated cancers, and have led to a Phase 1b/2 combination therapy study of lifirafenib and mirdametinib in solid tumor patients with K‐RAS mutations and other MAPK pathway aberrations.
The reduced sensitivity of K‐RAS‐mutated cancer cells to MEK inhibitors (MEKi), such as selumetinib and mirdametinib, is associated with feedback phosphorylation of MEK by upstream RAF reactivation. RAF dimer inhibitors, such as lifirafenib and compound C, in combination with MEKi potently suppress RAF‐dependent MEK phosphorylation and lead to sustained inhibition of MAPK signaling and tumor growth.
Phenylketonuria (PKU) is a common, congenital, autosomal recessive, metabolic disorder caused by Phenylalanine hydroxylase (PAH) variants.
967 PKU patients from Gansu, China were genotyped by Sanger ...sequencing, multiplex ligation-dependent probe amplification, and whole exome sequencing. We analyzed the variants of PAH exons, their flanking sequences, and introns.
The detection of deep intronic variants in PAH gene can significantly improve the genetic diagnostic rate of PKU. The distribution of PAH variants among PKU subtypes may be related to the unique genetic background in Gansu, China.
The identification of PAH hotspot variants will aid the development of large-scale neonatal genetic screening for PKU. The five new PAH variants found in this study further expand the spectrum of PAH variants. Genotype-phenotype correlation analysis may help predict the prognosis of PKU patients and enable precise treatment regimens to be developed.
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