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Sign In. Close mobile search navigation. This Site. Google Scholar. The American Society of Hematology. We did not notice obvious morphological changes except in fancp gene-inactivated fish, which were smaller in length. However, all mutant fish were either exclusively or in majority male.
Unlike reduced fertility among FA patients, all adult mutant fish were fertile, except for the fancd1 and fancj knockout males. These mutant zebrafish will serve as a huge resource for the scientific community to study the role of FA proteins in fish development, DNA repair, and as models for FA disease. PLoS Genet 14 12 : e This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.
The work is made available under the Creative Commons CC0 public domain dedication. Data Availability: All relevant data are within the paper and its Supporting Information files. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Fanconi anemia FA is a rare, mostly recessive, DNA repair deficiency disorder characterized by progressive bone marrow failure BMF , predisposition to cancer and developmental anomalies including hypogonadism and infertility [ 1 , 2 ].
BMF is an inevitable consequence of FA resulting in aplastic anemia due to the depletion of hematopoietic stem cells.
Expression of p. Considering that the c. We present a case of a patient with FA who developed a squamous cell carcinoma SCC of the tongue, along with a discussion of pertinent management considerations relevant to the head and neck clinician. The known business must be between 7 and 9 apps somewhat argued including to LNCS books. Remove From Wishlist Cancel.
The age of onset of anemia is variable but typically is in the first decade [ 4 ]. An increased predisposition to solid tumors, particularly head and neck squamous cell carcinoma HNSCC , esophageal and gynecological tissues is associated with FA [ 1 , 5 ]. Thus, FA is phenotypically a heterogeneous disease [ 9 ].
Our understanding of the disease is continually evolving as three of these genes were reported within the last two years [ 10 — 12 ].
Proper function of FA proteins has been shown to be important in maintaining hematopoietic stem cells, guarding genomic integrity, and preventing tumorigenesis [ 6 , 13 ]. Additional roles for FA proteins are emerging in aging [ 14 ], telomere biology [ 15 ], and selective autophagy and inflammation [ 16 ]. Animal models to help understand the molecular basis of FA clinical presentations and help explore the role of FA proteins in critical biological functions are needed. Biochemical and genetic studies have revealed to some extent the structural and functional components of the FA pathway [ 6 , 12 , 17 — 23 ].
Subsequent nucleolytic processing leads to translesion synthesis by a DNA polymerase FANCV , and the repair process is completed by homologous recombination. Only a fraction of FA gene homologs are present in any invertebrate model organism [ 24 , 25 ], limiting the utility of these models. We also targeted two additional genes encoding FA-associated proteins faap and faap Here, we present our data on the generation of mutant fish, evaluation of the consequences of genomic indels at the mRNA level, and characterization of mutant fish phenotypes such as growth, viability, sex differentiation, and fertility.
The goal of our study was to analyze the in vivo functions of all known FA genes. We targeted 17 genes known to have disease-causing mutations in FA patients, and two genes encoding for FA-associated proteins S1 Table. Multiplexing was primarily based on the known interactions among the FA proteins and their specific roles in the FA pathway [ 18 — 21 ], and therefore we also generated multi-gene knockouts to study their combined effect Table 1. Seven groups of pooled sgRNAs, that were prescreened for activity, were injected to target these 19 genes, which included three groups each of two and three genes and a group of four genes.
The injected fish mosaic founders were screened for germline transmitting mutations in each of the co-injected genes by genotyping of embryos from their outbred progeny. By screening a total of 75 founder fish, we identified 59 germline transmitting founders that passed multiple combinations of indel mutations in the co-injected genes. We outbred the selected founder fish with germline transmitting mutations to generate F1 fish heterozygous for frameshift mutations in each targeted gene.
These fish were genotyped at adulthood for each of the co-targeted genes. Our selection criteria for establishing mutant lines was to use either the F1 fish heterozygous for the desired mutant alleles in multiple genes or the F1 fish heterozygous for specific mutant alleles while carrying WT alleles at all other co-injected loci. We excluded any fish that were heterozygous for the desired allele but carried a non-desirable mutant allele, such as an in-frame indel mutation at the other co-injected loci, to avoid extensive genotyping in future generations.
We selected two frameshift mutations for each gene, except one each for fancb and fancd1 , resulting in a total of 36 single gene mutant alleles for the follow-up phenotypic analyses S2 Fig , S2 Table. Through our multiplexing effort, we were able to generate nine multi-gene mutant allele combinations across all seven injection groups S3 Table. An indel in the genomic sequence that is not a multiple of three is predicted to cause a frameshift in translation, therefore we confirmed the presence of each predicted mutation in the mRNA transcripts.
This effort would also reveal aberrant splicing caused by indel variants, if any. Details of splicing aberrations in these 4 cases are described below. The RT-PCR products for these mutants showed two bands, one matched expected size yellow arrows and the other was from an altered splice product red arrows.
PCR products were cloned and sequenced to determine aberrant splice product sequence. In hg41 mutant, the indel mutation 2 bp del in exon 12 results in partial skipping of mutated exon B. In hg42 mutant, the indel mutation 4 bp del in exon 1 results in partial use of new splice donor site in intron 1 C.
In hg45 mutant, the indel mutation 5 bp ins in exon 10 results in partial use of new splice acceptor and donor in exon 10 D. E The consequence on the predicted encoded protein based on the genomic indel mutation, and the observed aberrant splice product for all four mutant lines are shown. Sequencing revealed that the 25 bp insertion created a cryptic splice acceptor site leading to the deletion of 23 bp in the mRNA, resulting in a different frameshift mutation than predicted, still likely to cause a loss-of-function Figs 1E and S3B.
The intensity of the additional band in all three mutants was weaker, suggesting low abundance of the altered splice product. Nevertheless, it might be enough to have an effect on the phenotype by generating a low level of functional protein. To determine the effect of altered splicing on the reading frame and the encoded protein, we analyzed these RT-PCR products by cloning and sequencing.
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The altered splice product still generated a frameshift mutant protein p. The combined effect of a 4 bp deletion mutation near the end of exon 1 and the retention of 31 bp in the region adjacent to intron 1 generated an in-frame mutant protein with a deletion of 2 amino acids and an insertion of 11 unrelated amino acids p. The aberrant splice product generated an in-frame mutant protein with a deletion of 29 amino acids p.
This is particularly important if the mutant fish do not display any phenotype. It is important to validate that the frameshift mutant alleles lead to generation of truncated proteins as predicted and are therefore true loss-of-function alleles.
However, due to the absence of zebrafish antibodies or cross-species reacting antibodies for nearly all FA proteins, we could not evaluate protein expression in our mutants, except for Fancd2. Finding that a human FANCD2 antibody recognized its zebrafish counterpart, allowed us to confirm that the Fancd2 is not expressed in both fancd2 knockout lines, indicating that these are indeed null alleles S4 Fig.
As an alternate method, we used a recently described functional fluorescent mutation reporter assay [ 31 ] to test mutant alleles for a subset of genes: fance hg48 , fancf hg50 , fancg hg52 , fancl hg59 and fanct hg Despite robust control RFP expression, lack of GFP expression driven by the mutant allele, when compared to the WT allele, indicated that these frameshift mutations indeed introduce a premature stop codon S5 Fig. These data show that the mutant alleles for all five genes tested are true loss-of-function frameshift mutations.
In addition, as described below, we demonstrated hypersensitivity of nearly all frameshift mutant alleles to DEB treatment indicating that these are indeed null alleles. To determine if our mutants also exhibit similar hypersensitivity, the embryos from inbred heterozygous mutants were treated with DEB. The homozygous knockouts from fancd1 hg45 , fancd2 hg47 , fanci hg54 , fancj hg56 and hg57 , fancn hg62 , fancp hg66 and fanct hg70 mutant lines showed severe morphological changes compared to their WT and heterozygote clutch mates, indicating their hypersensitivity to DEB Fig 2A.
However, similar hypersensitivity was not distinct for the remaining mutants, possibly due to the protection provided by wildtype maternal transcript. To test this, we set up fanca hg41 homozygous mutant incross, as both male and female were available, and also outcross with wildtype counterparts. Untreated embryos from all three crosses looked normal.
Hypersensitivity to DEB treatment was observed among all the embryos from incross, and most embryos from female mutant outcross despite all being heterozygotes.