• Title/Summary/Keyword: DNA homology

Search Result 688, Processing Time 0.028 seconds

Control of Trophoblast Gene Expression and Cell Differentiation

  • Cheon, Jong-Yun
    • 대한생식의학회:학술대회논문집
    • /
    • 2001.03a
    • /
    • pp.195-205
    • /
    • 2001
  • 태반 영양배엽 (trophoblast)은 포유동물의 발생과정 중 가장 먼저 분화되는 세포로서, 자궁환경내에서 배아가 착상, 발생, 및 분화하기 위해서 반드시 필요한 태반을 형성하는 색심적인 세포이다. 영양배엽 세포의 분화과정중의 결함은 배아의 사산이나 임신질환 등의 치명적 결과를 초래한다. 하지만, 영양배엽 세포의 분화를 조절하는 분자생물학적인 메카니즘은 아직 규명되지 않고 있다. 영양배엽 세포의 분화를 조절하는 경로를 규경하기 위한 선결과제는 분화된 영양배엽 세포에서만 발현하는 많은 유전자들이 밝혀져야만 한다. 본 연구팀은 최근에 분화된 영양배엽 세포에서만 발현하는 두 종류의 새로운 유전자들을 찾았다. 한 종류는 homeobox를 보유하고 있는 조절 유전자 Psx이고, 다른 한 종류는 임신호르몬인 태반 프로락틴 라이크 단백질 유전자 PLP-C${\beta}$이다. 본 연구과제의 목표는 이들 유전자의 기능과 조절 메카니즘을 규명함으로써, 영양배엽 세포의 분화를 조절하는 조절경로를 밝히는 것이다. 이를 위하여 다음과 같은 일련의 연구를 수행할 것이다. 1) Psx 유전자가 분화된 영양배엽 세포에서만 발현케 하는 조절 메카니즘을 규명하기 위해 functional assays, in vitro footprinting, gel mobility shift assays, 생쥐형질전화, UV crosslinking, Southwestern blot 등의 방법을 통해 Psx 유전자의 cis-acting 요인과 trans-acting factor를 밝혀 분석한다. 2) 영양배엽 세포의 분화조절 경로를 규명하기 위해 random oligonuclotide library screening, DD-PCR, subtractive screening 등의 방법을 이용하여 Psx 유전자에 의해 조절되는 하부유전자를 밝힌다. 3) Psx 유전자를 knock-out시켜 영양배엽 세포가 발달 및 분화하는데 미치는 역할을 밝힌다. 4) Yeast two-hybrid screening방법을 이용하여 태반 프로락틴 유전자의 수용체를 찾아 이들의 신호전달 기전을 밝힌다. 제1차년 연구결과로서, mouse와 rat으로부터 각각 Psx 유전자의 genomic DNA를 클로닝하여, 유전자 구조를 비교한 결과, mouse Psx (mPsx2)는 4개의 exons으로 이루어져 있는 반면에, rat Psx (Psx3)는 3개의 exons으로 구성되어 있었다. 즉, rPsx3는 mPsx2의 exon1이 없었다. Notrhern blot과 in situ hybridization 분석에 의해 mouse와 rat에서 Psx 유전자가 다르게 발현 조절되는 현상을 밝혔다. 실제로 mPsx2와 rPsx3의 5'-flanking지역을 클로닝하여 염기서열 분석 결과 전혀 homology를 찾을 수 없었다. 또한, 이들 각각 promoter의 activity를 luciferase reporter를 이용하여 조사한 결과 Rcho-1 trophoblast cells에서 각기 다른 activity를 보여 주는 것을 발견하였다. Psx 유전자의 transcription start sites는 Primer extension에 의해 밝혔다. 또한 Psx2 유전자를 knock-out 시키기 위해 targeting vector를 Osdupde1에 제작하였다. 본 과제를 시작할 때 새로운 프로락틴 유전자 하나를 클로닝하여 이 유전자를 PLP-I라고 이름을 붙였다. 이 후 이 유전자 (PLP-I)는 PLP-C${\beta}$라고 이름을 붙이게 되었다. Mouse PLP-C${\beta}$ 유전자의 counterpart를 rat에서 찾아 염기서열을 비교한 결과 mouse와 rat에서 PLP-C${\beta}$유전자의 homology는 약 79% (amino acid level)였다. 본 연구과정을 통해 또 하나의 새로운 PLP-C subfamily member를 mouse로부터 클로닝 하였고, 이 유전자를 PLP-C${\gamma}$라 하였다. PLP-C${\beta}$와 PLP-C${\gamma}$의 발현 유형은 Northern blot과 in 냐셔 hybridization 분석에 의해 태반의 제한된 spongitrophoblast와 trophoblast giant cells에서만 발현하는 것을 밝혔다. 놀랍게도 이들 두 새로운 유전자는 alternative splicing에 의해 두 종류의 isoform이 있음을 밝혔다. PLP family member 유전자로서 splicing에 의한 isoforms을 보여 주는 유전자로는 PLP-C${\beta}$와 PLP-C${\gamma}$가 최초이다. 이들 isoform mRNAs의 발현 유형은 RT-PCR 방법을 이용하여 규명하였다. 또 하나의 새로운 발견은 PLP-C${\beta}$와 PLP-C${\gamma}$가 독특한 유전자 구조를 갖고 있었다. 즉, PLP-C${\beta}$는 exon3의 alternative splicing에 의해 5개 혹은 6개의 exons을 갖는 two isoforms이 생긴다. 반면에 PLP-C${\gamma}$는 exon2가 alternative splcing이 되면서 7개의 exons을 갖거나 6개의 exons을 갖는 isoforms을 만든다. 그리고, PLP-C${\gamma}$의 promoter activity를 trophoblast Rcho-l${\gamma}$ 세포주를 이용하여 PLP-C${\gamma}$ 의 1.5 kb 5'-flanking 지역이 trophoblast-specific promoter activity를 갖고 있음을 밝혔다. PLP-C${\gamma}$ 유전자의 transcription start site는 Primer extension에 의해 밝혔다. 제 1차 년도의 연구결과를 토대로, 2차년에서는 다음단계의 연구를 수행하고자 한다. 즉, 1) mPsx2와 rPsx3의 promoter를 비교분석 함으로서 mouse와 rat에서 Psx 유전자가 다르게 조절되는 메카니즘 규명, 2) Psx와 PLP-C 유전자의 promoter에 있는 cis-acting elements 탐색, 3) Psx2와 Psx3의 단백질을 이용하여 이들이 binding하는 target sequence 규명, 4) 제작한 Psx2 targeting vector를 이용하여 ES cells에서 Psx2 유전자 knock-out, 5) Psx 유전자를 과발현시키는 세포주를 만들고 Psx에 의해 조절되는 유전자 탐색, 6) 새로 밝히 PLP-C members 유전자들의 조절기전을 Rcho-1 세포주를 이용하여 여러 거지 성장인자와 다른 호르몬에 대한 반응을 탐색, 7) Psx와 PLP-C${\gamma}$ 유전자의 chromosomal mapping 등을 밝힐 것이다.

  • PDF

Identification and Sequence Analysis of RNA3 of a Resistance-Breaking Cucumber mosaic virus Isolate on Capsicum annuum

  • Lee Mi-Yeon;Lee Jang-Ha;Ahn Hong-Il;Yoon Ju-Yeon;Her Nam-Han;Choi Jang-Kyung;Choi Gug-Seon;Kim Do-Sun;Harn Chee-Hark;Ryu Ki-Hyun
    • The Plant Pathology Journal
    • /
    • v.22 no.3
    • /
    • pp.265-270
    • /
    • 2006
  • Cultivated hot pepper crops showing severe mosaic symptom were found in Korea in 2004 and their causal agent was identified as Cucumber mosaic virus (CMV). These pepper crops was resistant to the virus in the filled, and they belonged to pathotype 0 (P0) resistant pepper. Resistance screening of selected pepper plants showed that a pepper isolate of CMV was the P0 resistance-breaking virus. This P0 resistance-breaking isolate of CMV, named as Ca-P1, was isolated from leaves of the virus-infected Capsicum annuum cv. Manidda that showed systemic severe mosaic symptom. Ca-P1-CMV could induce systemic mosaic symptoms on P0-susceptible (P0-S) and P0-resistant (P0-R) cultivars whereas an ordinary strain (Fny-CMV) could not infect P0-R. This result suggests that Ca-P1-CMV can overcome P0 resistant pepper cultivars. To analyze its genome sequence, the complete nucleotide sequence of RNA3 of Ca-P1-CMV was determined from the infectious full-length cDNA clone of the virus. RNA3 of Ca-P1-CMV consisted of 2,219 nucleotides. Overall sequence homology of RNA3-encoded two viral proteins (movement protein and coat protein) revealed high similarity (75.2-97.2%) with the known CMV strains. By sequence analysis with known representative strains of CMV, Ca-P1-CMV belongs to a typical member of CMV subgroup IB. The resistance and resistance-breaking mechanisms of pepper and counterpart CMV, respectively, remain to be investigated, which will enrich the genetic resources and accelerate CMV-resistant pepper breeding programs.

Cloning and Expression of FSHb Gene and the Effect of $FSH{\beta}$ on the mRNA Levels of FSHR in the Local Chicken

  • Zhao, L.H.;Chen, J.L.;Xu, H.;Liu, J.W.;Xu, Ri Fu
    • Asian-Australasian Journal of Animal Sciences
    • /
    • v.23 no.3
    • /
    • pp.292-301
    • /
    • 2010
  • Follicle-stimulating hormone (FSH) is a pituitary glycoprotein hormone that is encoded by separate alpha- and betasubunit genes. It plays a key role in stimulating and regulating ovarian follicular development and egg production in chicken. FSH signal transduction is mediated by the FSH receptor (FSHR) that exclusively interacts with the beta-subunit of FSH, but characterization of prokaryotic expression of the FSHb gene and its effect on the expression of the FSHR gene in local chickens have received very little attention. In the current study, the cDNA fragment of the FSHb gene from Dagu chicken was amplified using reverse transcription polymerase chain reaction (RT-PCR), and inserted into the pET-28a (+) vector to construct the pET-28a-FSHb plasmid. After expression of the plasmid in E. coli BL21 (DE3) under inducing conditions, the recombination protein, $FSH{\beta}$ subunit, was purified and injected into the experimental hens and the effect on the mRNA expression levels of the FSHR gene was investigated. Sequence comparison showed that the coding region of the FSHb gene in the local chicken shared 99%-100% homology to published nucleotides in chickens; only one synonymous nucleotide substitution was detected in the region. The encoded amino acids were completely identical with the reported sequence, which confirmed that the sequences of the chicken FSHb gene and the peptides of the $FSH{\beta}$ subunit are highly conserved. This may be due to the critical role of the normal function of the FSHb gene in hormonal specificity and regulation of reproduction. The results of gene expression revealed that a recombinant protein with a molecular weight of about 19 kDa was efficiently expressed and it was identified by Western blotting analysis. After administration of the purified $FSH{\beta}$ protein, significantly higher expression levels were demonstrated in uterus, ovary and oviduct samples (p<0.05). These observations suggested that the expressed $FSH{\beta}$ protein possesses biological activity, and has a potential role in regulation of reproductive physiology in chickens.

Cashmere growth control in Liaoning cashmere goat by ovarian carcinoma immunoreactive antigen-like protein 2 and decorin genes

  • Jin, Mei;Zhang, Jun-yan;Chu, Ming-xing;Piao, Jun;Piao, Jing-ai;Zhao, Feng-qin
    • Asian-Australasian Journal of Animal Sciences
    • /
    • v.31 no.5
    • /
    • pp.650-657
    • /
    • 2018
  • Objective: The study investigated the biological functions and mechanisms for controlling cashmere growth of Liaoning cashmere goat by ovarian carcinoma immunoreactive antigen-like protein 2 (OCIAD2) and decorin (DCN) genes. Methods: cDNA library of Liaoning cashmere goat was constructed in early stages. OCIAD2 and DCN genes related to cashmere growth were identified by homology analysis comparison. The expression location of OCIAD2 and DCN genes in primary and secondary hair follicles (SF) was performed using in situ hybridization. The expression of OCIAD2 and DCN genes in primary and SF was performed using real-time polymerase chain reaction (PCR). Results: In situ hybridization revealed that OCIAD2 and DCN were expressed in the inner root sheath of Liaoning cashmere goat hair follicles. Real-time quantitative PCR showed that these genes were highly expressed in SF during anagen, while these genes were highly expressed in primary hair follicle in catagen phase. Melatonin (MT) inhibited the expression of OCIAD2 and promoted the expression of DCN. Insulin-like growth factors-1 (IGF-1) inhibited the expression of OCIAD2 and DCN, while fibroblast growth factors 5 (FGF5) promoted the expression of these genes. MT and IGF-1 promoted OCIAD2 synergistically, while MT and FGF5 inhibited the genes simultaneously. MT+IGF-1/MT+FGF5 inhibited DCN gene. RNAi technology showed that OCIAD2 expression was promoted, while that of DCN was inhibited. Conclusion: Activation of bone morphogenetic protein (BMP) signaling pathway up-regulated OCIAD2 expression and stimulated SF to control cell proliferation. DCN gene affected hair follicle morphogenesis and periodic changes by promoting transforming growth $factor-{\beta}$ ($TGF-{\beta}$) and BMP signaling pathways. OCIAD2 and DCN genes have opposite effects on $TGF-{\beta}$ signaling pathway and inhibit each other to affect the hair growth.

Definition of the peptide mimotope of cellular receptor for hepatitis C virus E2 protein using random peptide library (Random peptide library를 이용한 C형 간염바이러스 E2 단백질 세포막 수용체의 peptide mimotope 규명)

  • Lee, In-Hee;Paik, Jae-Eun;Seol, Sang-Yong;Seog, Dae-Hyun;Park, Sae-Gwang;Choi, In-Hak
    • IMMUNE NETWORK
    • /
    • v.1 no.1
    • /
    • pp.77-86
    • /
    • 2001
  • Background: Hepatitis C virus(HCV), a family of Flaviviridae, has a host cell-derived envelope containing a positive-stranded RNA genome, and has been known as the maj or etiological agent for chronic hepatitis, hepatic cirrhosis, and hepatocellular carcinoma. There remains a need to dissect a molecular mechanism of pathogenesis for the development of therapeutic and effective preventive measure for HCV. Identification of cellular receptor is of central importance not only to understand the viral pathogenesis, but also to exploit strategies for prevention of HCV. This study was aimed at identifying peptide mimotopes inhibiting the binding of E2 protein of HCV to MOLT-4 cell. Methods: In this study, phage peptide library displaying a random peptides consisting of 7 or 12 random peptides was employed in order to pan against E2 protein. Free HCV particles were separated from the immune complex forms by immunoprecipitation using anti-human IgG antibody, and used for HCV-capture ELISA. To identify the peptides inhibiting E2-binding to MOLT-4 cells, E2 protein was subj ect to bind to MOLT-4 cells under the competition with phage peptides. Results: Several phage peptides were selected for their specific binding to E2 protein, which showed the conserved sequence of SHFWRAP from 3 different peptide sequences. They were also able to recognize the HCV particles in the sera of HCV patients captured by monoclonal antibody against E2 protein. Two of them, showing peptide sequence of HLGPWMSHWFQR and WAPPLERSSLFY respectively, were revealed to inhibit the binding of E2 protein to MOLT-4 cell efficiently in dose dependent mode. However, few membrane-associated receptor candidates were seen using Fasta3 programe for homology search with these peptides. Conclusion: Phage peptides containing HLGPWMSHWFQR and WAPPLERSSLFY respectively, showed the inhibition of E2-binding to MOLT-4 cells. However, they did not reveal any homologues to cellular receptors from GenBank database. In further study, cellular receptor could be identified through the screening of cDNA library from MOLT-4 or hepatocytes using antibodies against these peptide mimotopes.

  • PDF

Human lactoferrin efficiently targeted into caprine beta-lactoglobulin locus with transcription activator-like effector nucleases

  • Yuan, Yu-Guo;Song, Shao-Zheng;Zhu, Meng-Ming;He, Zheng-Yi;Lu, Rui;Zhang, Ting;Mi, Fei;Wang, Jin-Yu;Cheng, Yong
    • Asian-Australasian Journal of Animal Sciences
    • /
    • v.30 no.8
    • /
    • pp.1175-1182
    • /
    • 2017
  • Objective: To create genetically modified goat as a biopharming source of recombinant human lacotoferrin (hLF) with transcription activator-like effector nucleases. Methods: TALENs and targeting vector were transferred into cultured fibroblasts to insert hLF cDNA in the goat beta-lactoglobulin (BLG) locus with homology-directed repair. The gene targeted efficiency was checked using sequencing and TE7I assay. The bi-allelic gene targeted colonies were isolated and confirmed with polymerase chain reaction, and used as donor cells for somatic cell nuclear transfer (SCNT). Results: The targeted efficiency for BLG gene was approximately 10%. Among 12 Bi-allelic gene targeted colonies, five were used in first round SCNT and 4 recipients (23%) were confirmed pregnant at 30 d. In second round SCNT, 7 (53%), 4 (31%), and 3 (23%) recipients were confirmed to be pregnant by ultrasound on 30 d, 60 d, and 90 d. Conclusion: This finding signifies the combined use of TALENs and SCNT can generate biallelic knock-in fibroblasts that can be cloned in a fetus. Therefore, it might lay the foundation for transgenic hLF goat generation and possible use of their mammary gland as a bioreactor for large-scale production of recombinant hLF.

Identification and characteristics of DDX3 gene in the earthworm, Perionyx excavatus (팔딱이 지렁이(Perionyx excavatus) DDX3 유전자의 동정 및 특성)

  • Park, Sang Gil;Bae, Yoon-Hwan;Park, Soon Cheol
    • Journal of the Korea Organic Resources Recycling Association
    • /
    • v.23 no.1
    • /
    • pp.70-81
    • /
    • 2015
  • Helicases are known to be a proteins that use the chemical energy of NTP binding and hydrolyze to separate the complementary strands of double-stranded nucleic acids to single-stranded nucleic acids. They participate in various cellular metabolism in many organisms. DEAD-box proteins are ATP-dependent RNA helicase that participate in all biochemical steps involving RNA. DEAD-box3 (DDX3) gene is belonging to the DEAD-box family and plays an important role in germ cell development in many organisms including not only vertebrate, but also invertebrate during asexual and sexual reproduction and participates in stem cell differentiation during regeneration. In this study, in order to identify and characterize DDX3 gene in the earthworm, Perionyx excavatus having a powerful regeneration capacity, total RNA was isolated from adult head containing clitellum. Full length of DDX3 gene from P. excavatus, Pe-DDX3, was identified by RT-PCR using the total RNA from head as a template. Pe-DDX3 encoded a putative protein of 607 amino acids and it also has the nine conserved motifs of DEAD-box family, which is characteristic of DEAD-box protein family. It was confirmed that Pe-DDX3 has the nine conserved motifs by the comparison of entire amino acids sequence of Pe-DDX3 with other species of different taxa. Phylogenetic analysis revealed that Pe-DDX3 belongs to a DDX3 (PL10) subgroup of DEAD-box protein family. And it displayed a high homology with PL10a, b from P. dumerilii.

Cloning and High Expression of Nattokinase Gene from Bacillus subtilis BB-1 (Bacillus subtilis BB-1으로부터 나토키나아제 유전자 크로닝 및 대량발현)

  • Lee Young-Hoon;Lee Sung-Ho;Park Ki-Hoon;Choi Young-Ju;Jeong Yong-Kee;Gal Sang-Wan
    • Journal of Life Science
    • /
    • v.16 no.2 s.75
    • /
    • pp.274-281
    • /
    • 2006
  • A fibrinolytic enzyme gene was isolated from Bacillus subtilis BB-1 by PCR method. Primers for PCR cloning were designed according to pre-identified gene for fibrinolytic enzymes from B. subtilis. The primer sequences were 5'-CGG ATC CGT GAG AGG CAA AAA GGT G-3' and 5'-TGA ATT CTT AAT GTG CTG CTG CTT GTC C-3' as concensus sequences of the fibrinolytic genes of Bacillus species. The PCR product was 1,145 bp and the sequence homology was 99% with nattokinase gene isolated from Japanese natto. The cloned fibrinolytic gene was reconstructed in Bacillus-E. coli shuttle vector, pEB for bulk-production. The fibrinolytic enzyme was purified by FPLC from the cloned B. subtilis 168. The optimum pH and temperature of the enzyme were 7.0 and $35^{\circ}C$, respectively. The fibrinolytic enzyme did not show any activity toward to skim milk, gelatin, casein and blood agar plate. The enzyme specific polyclonal antibody was prepared in rabbit for further assays such as detection of the gene expression in plant cells. This means that the enzyme may be used for health-care such as thrombosis without any hamful effects in the blood vessel.

Endometrium from Women with Endometriosis Expresses Increased Levels of Pleiotrophin (PTN) and Midkine (MK) mRNA Compared to Normal Endometrium (자궁내막증 환자와 정상 여성의 자궁내막에서 Pleiotrophin (PTN)과 Midkine (MK) mRNA 발현 차이에 관한 연구)

  • 정혜원;허성은;문혜성
    • Development and Reproduction
    • /
    • v.4 no.1
    • /
    • pp.101-108
    • /
    • 2000
  • Objectives: The pleiotrophin (PTN) and midkine (MK) are secreted heparin-binding neurokines that share 50% sequence homology. PTN and MK are expressed in the range of primary human tumors. The association of PTN and MK with carcinogenesis, enhancement of plasminogen activator activity and angiogenic factor are reported. Patients with endometriosis are characterized by the ability of the endometrium to implant; angiogenic and growth factors may play a significant role in the pathogenesis of endometriosis. To test the hypothesis that higher expression of PTN and MK in endometrium from women with endometriosis might be increase angiogenesis and growth ectopic endometriosis implants, we investigated PTN and MK expression by quantitative and competitive polymerase chain reaction (QC-PCR) in endometrium from women with and without endometriosis throughout the menstrual cycle. Design: MK and PTN mRNA expression in endomeoium from women with endometriosis and control patients without endometriosis were determined by QC-PCR throughout the menstrual cycle. Methods: Endometrial tissue was obtained from 25 patients with severe endometriosis and 30 patients without endometriosis undergoing hysterectomy or endometrial biopsy. Stage of endometrial cycle and a diagnosis of endometriosis were confirmed histologically. Total RNA was extracted and reverse transcribed into c-DNA. QC-PCR was performed to evaluate PTN and MK mRNA expression. Results were analysed by Post Hoc test. Results: MK and PTN were expressed throughout the menstrual cycle in both groups. MK expression was higher in follicular phase than luteal phase in endometrium from normal women. endometrium from endometriosis patients showed increased expression of PTN and MK compared to endometrium from normal women in the luteal phase (p<0.05). Conclusion: Our results suggest that uterine endometrium from women with endometriosis expresses higher levels of MK and PTN than endometrium from normal women during luteal phase. Increased MK and PTN expression may be related to the initiation of ectopic endometrial implants and their subsequent peritoneal invasion.

  • PDF

Molecular Cloning of Glycoside Hydrolase Family 74 Genes and Analysis of Transcript Products from the Basidiomycete Phanerochaete chrysosporium (담자균 Phanerochaete chrysosporium으로부터 유래한 Glycoside Hydrolase Family 74 유전자 클로닝과 전사산물 분석)

  • Lee, Jae-Won;Samejima, Masahiro;Choi, In-Gyu
    • Journal of the Korean Wood Science and Technology
    • /
    • v.34 no.3
    • /
    • pp.56-63
    • /
    • 2006
  • In order to evaluate the mechanism of cellulose hydrolysis, the complementary DNA encoding Glycoside Hydrolase Family (GHF)74 was cloned from Phanerochaete chrysosporium. Depending on the presence of Cellulose Binding Module (CBM), it can be classified as GHF74A or GHF74B. The GHF74A gene from P. chrysosporium (PcGHF74A) consists of 2163 bp encoding a protein of 721 amino acid residues. The PcGHF74A showed homology of 70~77% compared with the GHF74 from other filamentous fungi. The PcGHF74B, which contains CBM and is a member of family 1, was transcribed to various transcripts depending on the nature of carbon sources and their concentration. To study the possible presence of splice variants in GHF74B transcripts in P. chrysospoium, we carried out RT-PCR analysis using primers that designed based on the annotation data and sequenced data. Our result indicated that PcGHF74B was transcribed to several splicing variants in various culture conditions. Especially in the culture of 2% cellulose, three transcript products were observed. First transcript was presumed to be a full length ORF that contained 11th intron with stop codon at position 2562 bp. The second one consisted of 12 exons and 11 introns with stop codon at position 1187 bp with 7th exon. The shortest transcript consisted of 10 exons and 9 introns with stop codon at 910 bp in the 7th exon. These premature stop codon might prevent the synthesis of fully active GHF74 or contribute for the production of protein with distinct function depending on the ambient carbon sources.